Reducing Unintended Pregnancies as a Strategy to Avert Zika-Related Microcephaly Births in the United States: A Simulation Study

Katherine A. Ahrens, Jennifer A. Hutcheon, Loretta Gavin, Susan Moskosky

Introduction There is increasing evidence that infection with the Zika virus (ZIKV) during pregnancy can lead to severe brain abnormalities in infants exposed in utero. The objective of our analysis was to estimate the contribution of enhanced contraception access to averting ZIKV-related microcephaly births in the United States, alone and in combination with another possible strategy, anti-ZIKV vaccination. Methods We used Monte Carlo sampling techniques (n = 100,000 simulations) to estimate the number of microcephaly births expected under strategies of enhanced contraception only, vaccination only, both enhanced contraception and vaccination, and status quo (no intervention). Enhanced contraceptive access was assumed to reduce unintended pregnancy rates by 46% and anti-ZIKV vaccination was assumed to be 90% effective. Plausible values for effectiveness of enhanced contraceptive access, ZIKV cumulative incidence, ZIKV-related microcephaly risk, and anti-ZIKV vaccination parameters were derived from the literature or best available knowledge. Results Enhanced contraceptive access alone reduced the median number of ZIKV-related microcephaly births by 16% (95% simulation interval: 5, 23), while the anti-ZIKV vaccine alone reduced these births by 9% (95% SI: 0, 18), 45% (95% SI: 36, 54), and 81% (95% SI: 71, 91), under conservative (10% vaccine uptake), moderate (50% vaccine uptake), and optimistic (90% vaccine uptake) scenarios, respectively. The reduction in ZIKV-related microcephaly births was always greater if both interventions were employed. Discussion Enhanced contraceptive access alone has the ability to produce a meaningful reduction in microcephaly births, and could provide an important adjuvant prevention strategy even following the development of a highly-effective anti-ZIKV vaccine.