Vaccine
PREGNANCY RECOMMENDATION: Compatible
BREASTFEEDING RECOMMENDATION: Compatible
PREGNANCY SUMMARY
Although animal reproduction studies with anthrax vaccine adsorbed (AVA) have not been conducted, there appears to be no plausible biological mechanism for adverse pregnancy effects. Because of the absence of human pregnancy experience, however, the use of AVA during gestation is not recommended. The human reproduction data, limited to vaccination before conception, do not appear to suggest a risk from vaccination to either a woman’s subsequent fertility or a subsequent pregnancy outcome. However, the published study cited below lacked sufficient power to detect adverse birth outcomes (1). Until more data are available, the recommendation made by the CDC in 2000 and 2008 (2,3) that “pregnant women should be vaccinated against anthrax only if the potential benefits outweigh the potential risks to the fetus” is still relevant.
FETAL RISK SUMMARY
Anthrax vaccine adsorbed is prepared from a cell-free, noninfectious filtrate of Bacillus anthracis that contains a mix of cellular products adsorbed to aluminum hydroxide (2). This vaccine has replaced a previously available alum-precipitated vaccine. An avirulent, nonencapsulated strain (V770-NP10R) of B. anthracis is used in the production of the vaccine, which contains no dead or live bacteria (1,2). The cellular products in the vaccine include, in unknown amounts, three proteins known as protective antigen (PA), lethal factor (LF), and edema factor (EF). Live B. anthracis forms combinations of these proteins resulting in two exotoxins known as lethal toxin (PA and LF) and edema toxin (PA and EF). The recommended vaccination schedule is 0.5 mL at 0, 2, and 4 weeks; three booster vaccinations at 6, 12, and 18 months; and then an annual booster injection (2).
Reproduction studies with anthrax vaccine have not been conducted in animals (4). However, no plausible biological mechanism for an adverse effect on an embryo or fetus has been proposed (1).
The placental transfer of the three proteins contained in the vaccine has not been studied. Because of the very high molecular weight, simple diffusion does not appear to be possible for transfer.
Only one study has been located that examined the effects of anthrax vaccine, administered before conception, on pregnancy outcome (1). Women, aged 17–44 years, assigned to two U.S. Army installations formed the study population. During the study period from January 1999 to March 2000, 3136 women received at least one dose of the vaccine (most received two or three doses), whereas 962 women were not vaccinated. Departure from the study sites was the most common reason for not receiving the vaccine. The only acceptable medical indications to defer or refuse the vaccine were pregnancy or immunity-compromising disease. There were 385 pregnancies after at least one dose of the vaccine. The annualized pregnancy rates in those vaccinated and not vaccinated were 159.5 and 160.0 per 1000 person-years, respectively. These rates were nearly identical to the pregnancy rates before the study. Compared with unvaccinated women, vaccinated women were 1.2 times as likely to give birth (95% confidence interval [CI] 0.8–1.8). Adjustment for marital status, race, and age did not change the odds ratio (OR). A total of 327 births (vaccinated and unvaccinated) were available for outcome analysis. Low birth weight (<2500 g) occurred in 11 cases (3.4%). After adjustment, the OR for vaccination and low birth weight was 1.3, 95% CI 0.2–6.4. Congenital malformations (specific details not provided) were observed in 15 cases, but no unusual patterns or clusters were noted. Only one malformation (polydactyly of the fingers) had multiple occurrences (three cases: two vaccinated, one unvaccinated). After adjustment, the OR for vaccination and structural anomalies was 0.7, 95% CI 0.2–2.3. The adjusted OR for vaccination and any adverse birth outcome was 0.9, 95% CI 0.4–2.4 (1).
BREASTFEEDING SUMMARY
No reports describing the use of anthrax vaccine in lactating women have been located. Because of the nature of anthrax vaccine, the potential for adverse effects in a nursing infant appear to be nil. The CDC states that there is no evidence to suggest a risk to the mother or nursing infant, and the administration of the vaccine during breastfeeding is not medically contraindicated (2,3).
References
1.Wiesen AR, Little CT. Relationship between prepregnancy anthrax vaccination and pregnancy and birth outcomes among US Army women. JAMA 2002;287:1556–60.
2.CDC. Use of anthrax vaccine in the United States. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 2000;49(No. RR15):11.
3.CDC. Guidelines for Vaccinating Pregnant Women. Available at http://www.cdc.gov/vaccines/pubs/preg-guide.htm. Accessed May 16, 2010.
4.CDC. Notice to readers: Status of U.S. Department of Defense preliminary evaluation of the association of anthrax vaccination and congenital anomalies. MMWR 2002;51(6):127.