TO THE EDITOR—Ritonavir-boosted nirmatrelvir (NMV/r) administration within 5 days of coronavirus disease 2019 (COVID-19) onset for people with mild or moderate COVID-19 who have risk factors for severe COVID-19 can significantly and substantially reduce the risk of hospitalization and death [1]. While the registrational trial enrolled only unvaccinated participants, the results of a real-world study reported in Clinical Infectious Diseases indicate that even in the era of Omicron, NMV/r is highly effective in reducing the risk of severe COVID-19 or mortality in people with risk factors for severe COVID-19, including those who have been vaccinated [2]. However, pregnant people were excluded from the registrational trial and the effectiveness study.

Pregnancy (including the post pregnancy period) increases the risk of severe or fatal COVID-19. In addition, pregnant and postpartum people may have other conditions that independently increase their risk of severe COVID-19 outcomes [3]. COVID-19 vaccination (including booster) is strongly recommended for adults who are, could become, or were recently pregnant; however, these groups of people, even if fully vaccinated, may still contract COVID-19 [3]. It is unacceptable that the manufacturer has failed to assess short-term safety and confirm comparable pharmacokinetics of NMV/r in pregnancy. These studies should be urgently completed so that people who are pregnant (or could become pregnant) and their physicians can make a more informed decision about use of NMV/r. Citing the lack of inclusion of pregnant and breastfeeding people in randomized clinical trials of NMV/r, the World Health Organization (WHO) has declared that clinicians should not consider use of