While some sexually transmitted diseases (STDs) are curable, others, including HIV, are not. The consequences of STDs can include ill health, infertility, compromised infant health, cancer and death. An estimated 15 million new cases of STDs occur yearly in the United States.1 Globally, annual new cases probably top 400 million.2 It is estimated that one-quarter to one-half of all Americans get an STD * in their lifetime.3

Women are physiologically more vulnerable to contracting an STD than men when they have unprotected intercourse with an infected partner. They often experience less obvious symptoms of infection than men, and therefore, may not seek care as quickly as men. As a consequence, they may experience more serious complications.4 Additionally, the gender inequities that exist in many cultures and societies may hinder women's ability to negotiate the conditions of their sexual lives and to insist that their partner use a condom.5

Furthermore, the technology available for preventing STD transmission leaves women at a disadvantage.6 While latex male condoms provide excellent protection against STDs, they are not always used consistently and correctly and are a male-controlled method. The polyurethane female condom shows promise for STD protection as well as contraception, but its use still depends on male cooperation and acceptance. Because of women's special biological susceptibility to sexually transmitted infection, their often disadvantaged position in gender relations and the limitations of available method options for disease prevention, the development of methods for preventing STDs that can be totally controlled by women is a high priority.7

Research is underway to develop safe and effective products, called microbicides, that women can use vaginally to prevent STD transmission.8 While it seems clear that current spermicidal contraceptives, which are all based on nonoxynol-9, reduce infection from some STDs, research is ongoing to understand their effects on HIV transmission.9 Other work focuses on reformulating nonoxynol-9 or combining it with new compounds and on alternate products that use completely new materials and approaches.10 However, the realities of clinical trials and of product development and approval mean that proven microbicides will probably enter the market no earlier than 2001.11

Researchers are just beginning to explore women's potential interest in using microbicides and their preferences regarding method characteristics. Such investigations can help indicate whether there will be a receptive market for microbicidal products and can inform development choices regarding method characteristics. A research project of the European Union's HIV/AIDS Programme in Developing Countries found that one-quarter of respondents in urban France and more than 70% in urban areas of Cote d'Ivoire, Kenya and South Africa think a vaginal microbicide would be very useful. In the sub-Saharan countries, more than half of the participants said they were prepared to pay up to five times the price of a condom for such a method.12 A survey of women in Brazil found that almost half of them were willing to pay up to $5 per application for a product that would prevent pregnancy and STDs.13 Focus groups conducted in New England and Puerto Rico among women involved in drug use (either personally or through their partner) suggested high levels of interest in using vaginal methods that would prevent HIV.14

Methodology

To find out how many women are interested in and likely to use vaginal microbicides, which groups of women would be most likely to use them and what women's preferences are regarding the characteristics of such products, we surveyed a nationally representative sample of 1,000 women in the continental United States aged 18-44 who had had sex with a man in the last 12 months. In preparation, we conducted in-depth personal interviews to explore many of the issues and questions being considered for inclusion on the national survey. These were conducted with more than 30 women recruited from Planned Parenthood and social service sites in California, New York and Wisconsin. We obtained information on interview length and item comprehension and clarity from a telephone pretest.

Survey Methods Group, Inc., of San Francisco, California, carried out surveying between January and May 1998. Experienced, trained female interviewers conducted the interviews over the telephone using a computer-assisted telephone interview system, which directly coded responses into the computer datafile. Interviews averaged 19 minutes in length. Thirty-seven were conducted in Spanish; all others were in English.

Survey Sampling, Inc., generated a random digit dial sample of 12,797 telephone numbers for this study. The sample was nationally representative of households throughout the continental United States. Of these numbers, 12,298 were dialed up to 12 times each, if necessary, to complete an interview or to take it to final disposition. In all, 8,102 potentially eligible households were identified, of which 5,097 were successfully screened for eligibility.

A total of 1,266 eligible respondents were identified and 1,000 completed the interview, for an overall cooperation rate of 79%. The level of cooperation may have been somewhat reduced because of the sensitive nature of the study, which, for informed consent purposes, was explained early in the screening process. The majority of the uncompleted interviews were refusals during the introduction (158) or uncompleted callbacks to eligible women (103). Only five women who began the interview did not complete it.

The survey included only women who were living in households with telephones. (Six percent of U.S. households have no telephone service,15 and they are generally poorer households.) There is no indication, however, that the respondents were biased in characteristics that would affect their interest in using microbicides or their product preferences. The proportions of respondents in age, marital status, and race or ethnicity subgroups were all within three percentage points of the proportions among sexually active women of similar age from the 1995 National Survey of Family Growth (NSFG).

Survey respondents were much more likely than NSFG respondents, however, to report that they had completed some college (64% vs. 47%, respectively). This may have been because women who live in households with no telephone were excluded from our survey or because respondents may have overstated their educational accomplishments. Alternatively, the difference may result from variations in questionnaire wording or in survey administration between this survey and the NSFG.

Analyses were performed using SPSS (Statistical Package for Social Sciences) for Windows, Version 6.1. The data were not weighted. Tests of significance for cross-tabular comparisons were performed using the Pearson chi-square test of independence. Logistic regression analysis was used to investigate multivariate predictors of interest in microbicides—using as the dependent variable the proportion of all women who reported being very interested in current use and who also were worried about getting an STD. The coefficients for this model were estimated using the maximum-likelihood method. We present the odds ratios and the level of significance for each coefficient based on the Wald statistic.

To estimate the number of potential microbicide users among women in the United States, we applied proportions from this survey to numbers of women in the NSFG who were aged 15-44 and who had had sex in the last 12 months. The NSFG number of women was not adjusted for population change because the estimated number of U.S. women aged 15-44 increased less than 1% between 1995-1998. Since our survey did not include respondents younger than age 18, we applied proportions from our survey for women aged 18-24 to the number of NSFG women aged 15-17 who had had sex in the last 12 months.

Findings

Background Characteristics

Most respondents were married or cohabiting, had some post-high school education and had children (Table 1). About three-quarters were non-Hispanic white, 12% non-Hispanic black, 9% Hispanic and 4% Asian or other races.

Three-quarters of respondents were contraceptive users or relied on their partner's method. The others were pregnant or trying to become pregnant or were using no method even though they were at risk of unintended pregnancy. Although only 5% of respondents currently used vaginal contraceptives, 40% reported having ever used such a method. Of these, a majority said that they were either very satisfied (23%) or somewhat satisfied (42%) with their past use of these methods (not shown).

STD Experience and Preventive Behaviors

Most women had basic knowledge about STDs. More than 80% knew that some STDs have no immediate symptoms, that some cannot be cured and that there are long-term health effects from some STDs other than HIV. However, 10-11% of women said they did not know these facts. Of greater concern, 8% thought that a woman can always tell if she has an STD, 9% that all STDs other than HIV can be cured with medication and 6% that there are no long-term health effects for women infected with most STDs.

Nearly one in five women reported having had some direct experience with STDs or having been concerned that they might have had an STD. About half of these (10%) said either that a doctor had told them that they had genital herpes or human papillomavirus (HPV) or that a partner had had an STD during the time that they were together. In all, 15% of women said they had gone to a doctor or clinic because they had symptoms they thought might be from an STD other than HIV (Table 1).

Thirteen percent of women reported either that they themselves had had more than one sexual partner in the last year (8%) or that they knew or suspected that their partner had had sex with another women within the past year (7%). Only 5% of married women said they had had more than one partner or thought their partner had had sex with another woman in the past year, compared with 21% of unmarried cohabiting women and 31% of other unmarried women (not shown). These reported responses about STD experience and risk behaviors should be viewed with caution and considered lower limits of the actual levels, however, since such sensitive behaviors are typically underreported in surveys.

A minority of respondents said they and their partners had taken some actions to lower their risk of sexually transmitted infection. Only 11% said they and their partner currently used condoms for disease protection—3% of married women, compared with 18% of cohabiting women and 33% of women not in a union. All but two of these 107 respondents said they were also using condoms for pregnancy prevention. An additional 38% of women said they had used condoms for protection against STDs in the past, again usually for both disease and pregnancy prevention, and 18% said they had ever stopped having sex for a period of time or had sex less often because they were worried about getting an STD (Table 1).

About three in 10 respondents said they were currently worried about getting an STD—5% were very worried, 10% were somewhat worried and 14% were a little worried (not shown). The majority of women, however, were currently not at all worried about becoming infected.

Women's Interest in Using Microbicides

Degree of interest. Prior to administering questions regarding vaginal microbicides, interviewers described such products to respondents. § Ninety-three percent of all respondents said they would be interested in using a vaginal microbicide if they ever found themselves in a situation where they might be at risk of contracting an STD.** Moreover, 80% of all women said they would have been interested in using such a product at some time in the past, if it had been available.††

Overall, 40% of women expressed any current interest in using a microbicidal product—16% were currently very interested, 13% were somewhat interested and 11% were a little interested. ‡‡ Ninety-two percent of women currently interested in using a microbicide said that a reason for their interest was that they wanted to be in control of protecting themselves. Other reasons reported by at least one-third of interested women included that they did not trust their partner to be monogamous or that either they or their partner did not like condoms. Most women (88%) who were not currently interested in using a microbicide said this was because they trusted their partner to be monogamous.

There was substantial overlap between being worried about getting an STD and being interested in using a microbicide. Twenty-four percent of women reported that they were both currently interested in using a vaginal microbicide and currently worried about contracting STDs (Table 1). Fifty-five percent said they were neither worried about getting an STD nor currently interested in using a microbicide (not shown).

The remaining women reported somewhat conflicting or mixed perspectives about their risk for getting an STD and their interest in using a microbicide. Five percent of women said they were worried about getting an STD but were not interested in using a microbicide. Conversely, 17% of women reported that they were currently interested in using a microbicidal product, even though they were not currently worried about STDs (Table 1).

Logistic regression analyses indicate that in both cases, women with conflicting perspectives were more likely to be married and less likely to report current condom use than were those who were both interested in microbicide use and currently worried about getting an STD. In addition, women who were interested in microbicide use but not worried about STDs were more likely to be cohabiting and to have higher incomes, and were less likely to have ever made a medical visit about STDs or to have ever stopped having sex because of concerns about STDs (not shown).

Subgroup differences. The biggest social or demographic differences in women's interest in using microbicides and their worry about getting an STD are related to marital status: Women who were not in a union were almost three times as likely as cohabiting women and 12 times as likely as married women to say that they were both worried about getting an STD and very interested in using vaginal microbicides (Table 1). Women who were younger, had a low income, were less-educated, were childless and were black or Hispanic also were significantly more likely than other women to report that they were currently interested in using microbicides and currently worried about contracting STDs.

A significantly higher proportion of women currently using nonpermanent contraceptive methods than women using sterilization reported a high level of interest in and a perceived need for a microbicide. However, women who had ever used a vaginal contraceptive method (jelly, cream, suppositories, film or the sponge) were only slightly more likely to report a high interest in using vaginal microbicides than were women who had never used such methods. Finally, 38% of those currently using condoms for STD prevention were both worried about getting an infection and very interested in microbicide use, compared with only 2% of those who never used condoms for STD prevention.

Women who said that their partners had had other partners in the past year were seven times as likely as the others to be very interested in using microbicides, and women who themselves reported multiple partners in the past year were almost five times as likely as other women to be very interested in microbicides and to be worried about getting STDs. In addition, respondents who said a partner had had an STD and those who had ever been tested for STD symptoms were about three times as likely as other respondents to be currently worried about STDs and to have a very high interest in using microbicides.

Underreporting of women's past experience with STDs and their behaviors related to the risk of contracting STD implies that the observed impact of these variables on their interest in using microbicides also is very likely underestimated.

Multivariate analysis. Logistic regression results (Table 1) indicate that the strongest independent predictor of whether a woman was worried about getting STDs and was very interested in using microbicides was whether she and her partner were already using condoms for STD prevention (odds ratio, 8.8) and whether they had done so in the past (odds ratio, 4.7).

Women who said they knew or suspected that their current partner had had sex with someone else in the past year were significantly more likely than those who said their partner was monogamous to be worried about STDs and to be very interested in using microbicides (odds ratio, 3.7). Women who had no steady partner in the last 12 months were also more likely to be in the category of high potential use of microbicides (odds ratio, 3.7). However, whether a woman reported having had more than one sexual partner herself in the past year was not significant when her reports of the man's behavior were in the model.

Women who said that they had gone to a doctor or a clinic in the past with concerns about STD symptoms were significantly more likely than other women to be currently worried about contracting STDs and to be very interested in microbicides (odds ratio, 3.0). Reporting that they had had herpes or HPV or a partner with an STD were not statistically significant predictors, although the odds ratios remained somewhat elevated.

Low-income women and those with the least education were significantly more likely to be worried about STDs and very interested in microbicide use, as were black and Hispanic women. However, age and parity, which were significant in bivariate tabulations, were no longer significant in the multivariate analysis. Women who were not in a union were significantly more likely than married women to be worried about STDs and very interested in microbicide use (odds ratio, 3.9).

When the analysis was rerun including only the social and demographic variables, the odds ratio for women not in a union rose to 14.0, illustrating the fact that apparent effects of union status often reflect unmarried women's higher risk for STDs and their more frequent use of preventive behaviors. Cohabiting women were also significantly more likely than married women to be interested in microbicides in this limited regression analysis (odds ratio, 2.8; not shown).

Potential microbicide users' characteristics.
The distribution of women across subgroups of potential use status reflects both a group's level of interest in microbicides and worry about STDs and its size in the population. For instance, married women are least likely to be interested in using microbicides and to be worried about getting STDs, but they are a large proportion of sexually active women aged 18-44. As a result, they comprise 43% of all women with any interest in microbicides and almost one-fifth of those most likely to be potential users (Table 2). Similarly, while white non-Hispanic women are less likely than black or Hispanic women to be interested in microbicides, they make up 61% of all women with any interest and almost half of those most likely to use microbicides.

The largest proportions of women most likely to be potential users because they are currently worried about STDs and are very interested in using microbicides are those who are not in a union, are aged 25-34, have an annual family income less than $20,000, have not attended college, have one or more children and are non-Hispanic whites. They currently use a nonpermanent prescription method of contraception and are using or have used condoms for STD prevention in the past.

Preferences for Product Characteristics

Respondents who had expressed any interest in a microbicide (99%) were asked their preferences about method characteristics. We note all subgroup differences (significant at p<.05 using the chi-square test) at least 10 percentage points in size. In general, though, most preferences did not vary widely across subgroups.

Overall, two-thirds of women said they would prefer a microbicidal product that could be applied several hours prior to intercourse (Table 3).§§ Women aged 35-44 were more likely than those aged 18-24 to prefer a method that could be applied several hours before intercourse (73% vs. 60%); similarly, non-Hispanic white women (72%) were more likely than black or Hispanic women (56-57%) or other women (42%) to say so (not shown). Those with an annual family income of $40,000 or more also were more likely than women with an annual income of less than $20,000 to say they had a preference for early application (74% vs. 58%). There were no strong subgroup differences, however, in whether women would use a method that must be reapplied before every act of intercourse.*

Most women (71%) would prefer a product that could be purchased over the counter at a drugstore. One in seven, however, would prefer obtaining a prescription from a medical provider (Table 3).* During the personal interviews, these women said they would have more confidence in the product and in their ability to use it correctly if it was prescribed by a clinic or doctor. Women aged 35-44 were more likely to prefer a product they could get without a prescription (75%) than were those aged 18-24 (61%), as were women with annual incomes of $40,000 (78%) compared with those with annual incomes below $20,000 (61%, not shown). White women, as well as Asian or other women, also were more likely to prefer an over-the-counter product (75-79%) than were black and Hispanic women (55-62%).

Women were divided in their preferences for the form the product should take. Younger women were more likely to prefer a cream or jelly (54% of women aged 18-24 vs. 33% of those aged 35-44), while the older women more often preferred a suppository (35% vs. 21%, not shown). Although overall only one-third said that they would prefer a product that could be used without their partner's knowledge (Table 3), even fewer Hispanic women (24%) said they would prefer such a product, compared with 33-35% of black and white women (not shown).

Women's interest in using microbicidal products remained strong, even when the product was described as not 100% effective*§ or as effective at preventing HIV but not other STDs.* In each case, almost half of the women would remain very interested in using the product, and almost a third would be somewhat interested (Table 3). However, women's interest in the product was diminished when the potential microbicide was described as protecting against other STDs, but not against HIV. †‡

Women appeared quite willing to pay an amount equivalent to the cost of condoms ($0.50-1.00) for a microbicidal product.†§ When faced with a more expensive product ($2 per application),* the percentage remaining very interested in use dropped from 78% to 60%. While 66% of women aged 35-44 said they would be very interested in a microbicide costing $2 per application, this proportion fell to 53% among women aged 25-34 (not shown). Eighty percent of white and black women said they would be very interested if the product cost one dollar or less per application, but these proportions dropped to 59% and 67%, respectively, if the cost were $2 per use.

Most women (84%) said that if they used a microbicide, they would likely use it along with condoms to get added protection, rather than substituting it for condoms (Table 3).‡† Similarly, when presented with a version that also was effective in preventing pregnancy,‡§ nearly two-thirds (63%) responded that they would continue to use their other contraceptive method for pregnancy prevention, in addition to using microbicides for STD prevention. Women who were not in a union were more likely to say they would use a microbicide with their regular birth control method (68%) than were women who were married or cohabiting (57%; not shown).

Typically, women did not expect their sexual partners to be a hindrance to use of microbicidal products. However, almost one woman in five thought that her current partner would object if she wanted to use a microbicide (Table 3). Among the 48 women who said that they might need to use a microbicide with their current partner and that he would object to using this kind of product, 40 said they would use it anyway—19 without telling him and 21 even if he didn't want her to use it (not shown).

Women who were not in a union were more likely than married and cohabiting women to think that their partner would be happy for her to use a microbicide (47% vs. 18%) and less likely to think that he would object to their using a microbicide (6% vs. 21%). Low-income women and those aged 18-24 were more likely than high-income women and those aged 35-44 to think that their partner would be happy and less likely to think he would object. Non-Hispanic white women (18%) were less likely than black women (39%) or Hispanic and Asian or other women (32-33%) to think their partner would be happy with their using a microbicidal product.

Estimated Number of Potential Users

We estimated that as of 1998, 21 million of the nearly 60 million U.S. women aged 15-4416 would be interested at all in current microbicide use (Table 4), and that 15.5 million women are currently worried about contracting STDs (not shown). Some 12.6 million women are both currently worried about STDs and interested at all in using a microbicide; 6.0 million of these would be very interested in using such a method (Table 4). Even if the product provides only a 70-80% reduced risk of contracting STDs, 11.5 million of these women would be interested in current microbicide use, and 3.7 million women would be very interested.

Cost makes a difference in women's projected interest. The number of women who think they would be interested in using a microbicide even if it is less than 100% effective drops from 9.5 million if the product costs a dollar or less to 7.7 million if it costs $2 per application. At the higher price, 3.l million women would remain very interested in using such a product, even if it is not totally effective.

If the microbicide is less than 100% effective and only protects against HIV, 9.1 million women would be interested in using it at a cost of less than a dollar and 7.3 million would be at a cost of $2. At this higher cost and with potential product limitations, 2.5 million women would remain very interested in using a microbicide.

Discussion

The effort required to develop, test and bring to market new methods that women can use to prevent the transmission of STDs is great. The need for such methods, and their potential beneficial impact, also are great, both in the United States and worldwide. About three in 10 women of reproductive age in the United States are currently worried about getting an STD. However, only about one in 10 is currently using condoms to prevent an infection. Whether the potential for new methods is worth the work and expense they entail will depend on whether women at risk for contracting, or transmitting, these infections will use them.

A survey such as the one reported here should not be taken as an exact prediction of the numbers and characteristics of women who will use a vaginal microbicide when it becomes available, since women are reporting about a hypothetical method and do not have to take any actions toward its use. Further, survey responses cannot determine whether women who intend to try out a new product would be willing to continue using it. Still, such information is useful in determining whether the concept is of interest to women, how interested they are in it and which women are more likely to be potential users. Indeed, the results of this survey of sexually active women in the United States aged 18-44 indicates substantial concern about STDs and interest in the use of vaginal microbicides.

Four in 10 women said that they would be currently interested in using the type of vaginal microbicide presented to them, primarily because they want to be in control of protecting themselves from infection. Our data suggest that some 6.0 million women aged 15-44 are very interested in current use and are currently worried about getting an STD. These women are probably the most likely potential users of such a method. The strongest predictors of being a potential user are women's current use of condoms to prevent infection with STDs, their perception of exposure to risk, their being unmarried and not living with a man, and their being black.

Yet, women in all social and demographic subgroups showed some interest in vaginal microbicides and also were worried about STDs. Thus, it is likely that another 6.5 million women are worried about getting STDs and are somewhat or a little interested in microbicides.

The characteristics of the method will be especially important in determining how many women will use a microbicide. One in every six women in our survey said that they were currently interested in using a microbicide but were not now worried about getting STDs. A very attractive method and related public education and advertising might cause them to consider microbicide use, as well as to reassess their concern about infection.

The preferences of a majority of women mirror current considerations in method development (i.e., that the method can be applied well in advance of intercourse and that it is readily accessible over the counter rather than by prescription). Contrary to current thinking, only one-third of women said that they would prefer a product that could be used without their partner's knowledge. This is undoubtedly related to the fact that only one in five women thought their current partner would object to their using such a method. However, a method that could be used without the partner's knowledge would meet all women's needs, regardless of whether they would choose to tell their partner about microbicide use.

The ideal microbicide would be 100% effective against HIV and all other STDs and would be inexpensive. Such a method is of course unlikely to be produced any time in the foreseeable future. Women's responses in this survey indicate that the further a product is from this ideal, the less women will be interested in using it. However, women's views also suggest that their expectations are realistic, and are likely to match the types of products that will become available. Of the estimated 12.6 million women aged 15-44 interested in current use and worried about STDs, 11.5 million would still be interested in a method even if it is not 100% effective or 11.0 million would remain interested even if it does not protect against STDs other than HIV. In fact, fewer (but still a majority) would be interested if the method protected only against STDs other than HIV.

Women's predictions of their use of a microbicide were affected by potential price, but interest was still high at $2 per application. We estimate that more than seven million sexually active women aged 15-44 would be interested in a vaginal microbicide even if the product only protected against HIV, was only 70-80% effective and cost $2 per application; 2.5 million of them would be very interested in its use.

Since microbicides are unlikely to be 100% effective or to protect against all sexually transmitted infections, the possibility that women and their partners might abandon the use of condoms if such a product became available has raised concern. However, 84% of the women whom we surveyed said they would be likely to use a microbicide together with condoms for added protection, and 63% said that even if the microbicide also prevented pregnancy, they would still continue using another contraceptive method.

In the end, our findings offer two important insights. First, many American women are worried about STDs and think they would use a vaginal microbicide, even if it is not a perfect method. How many will use such methods when they become available remains to be seen, however, and depends on the methods themselves, on how they are presented to potential users and on users' perceptions of their own needs and of their risk for becoming infected.

In addition, even with relatively high levels of interest in microbicides among women at risk for STDs, there remain women who appear to be at risk but who are not interested in using this type of product. Thus, vaginal microbicides may be able to help some women reduce their susceptibility to sexually transmitted diseases, but it is unrealistic to believe that microbicides will be the complete answer. Action will continue to be needed to provide education about STD risks and the potential for infection, to improve women's status and to increase women's ability to act in their own best interests.