The benefits of maternal vaccination to a child through maternal antibody transfer across the placenta have long been recognized. In the 1870s, infants born to mothers who had been vaccinated against smallpox were less likely to have smallpox early in life.1 Tetanus toxoid vaccination during pregnancy, with improved hygiene during childbirth, is significantly lower in newborn tetanus in some developing countries.1 Risks of influenza and pertussis have been reported to decrease in the first few months of life in infants who received the mother’s inactivated influenza vaccine and combined tetanus-diphtheria-acellular pertussis (TDAP) vaccine, respectively. Both vaccines are routinely recommended during pregnancy in the United States; The influenza vaccine is recommended at any time during pregnancy, but the Tdap vaccine is preferred in the early part of pregnancy weeks 27 to 36 to maximize maternal antibody production, placental transfer, and antibody levels in the newborn.2 There are ongoing studies evaluating whether the maternal vaccine prevents illness in other infants (e.g., respiratory syncytial virus infection or group B streptococcus infection).1
At the time of the authorization of the Coronavirus Disease 2019 (Covid-19) vaccine, information on their use during pregnancy was limited because pregnant women were excluded from clinical trials. Since the time of power, safety data about vaccination during pregnancy has been rapidly accumulating.3,4 The results of the retrospective cohort study are now reported Journal5 No association was found between maternal vaccine and serious adverse events at 42 days after vaccination. Based on the increased risk of acute disease and pregnancy complications associated with Covid-19 during pregnancy,6 Safety data promising the use of other vaccines during pregnancy, and data on the safety of the Covid-19 vaccine for mothers and fetuses, disease control and prevention, and professional bodies (eg, American College of Obstetricians and Gynecologists) strongly recommend vaccination in pregnant women. Booster dose is also recommended after the completion of the initial vaccine series.
Given the experience of previous vaccines, the mother’s Kovid-19 vaccine is expected to provide some level of infant protection. Maternal antibodies have been shown to be present in umbilical cord blood, neonatal blood and breast milk after maternal Kovid-19 vaccination, but the correlation with infant protection from infection is unclear.6
Now in JournalPalza and colleagues7 Results of a large multicenter study using a case-control, test-negative design to assess the effectiveness of maternal vaccination versus hospitalization for Covid-19 in infants younger than 6 months. In this study, 16% of the 537 infants hospitalized for Covid-19 (case babies) were born to mothers who were fully vaccinated against Covid-19 during pregnancy. In contrast, 29% of the 512 hospitalized infants who had a negative test for acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (control infants) were born to mothers who were fully vaccinated during pregnancy. The efficacy of maternal vaccine against covidin-19-related hospitalization in infants was 52%. Vaccine efficacy increased by 70% against admission to the intensive care unit for Covid-19. The present report extends previous findings of this population8 To add an additional 670 infants, many of them were hospitalized during the circulation of the Omicron mutation. As expected, vaccine efficacy was lower during circulation of the omicron mutation than the delta-prime period (38% vs. 80%). In addition, the efficacy of the vaccine is higher when the second dose of the covid-19 vaccine is given after 20 weeks of pregnancy (69% vs. 38%).
The results of a study by Halasa et al. Provide strong evidence that maternal vaccination is effective in reducing the risk of covid-19-related hospitalization in infants younger than 6 months, further supporting the covid-19 vaccination recommendations during pregnancy. Such infants are at greater risk for severe illness and hospitalization than older children and cannot be vaccinated now or in the future. Because vaccines are less effective in infants younger than 6 months,1 Recently completed clinical trials of covid-19 vaccines in young children have excluded that age group.
This study also raises the question of the optimal timing of covid-19 vaccination during pregnancy. Determining the optimal timing is difficult because given the high risk of severe Covid-19 during pregnancy, the benefits of maximizing infant protection against maternal risks of delaying vaccination should be balanced. Further studies are needed to determine whether the additional booster dose given during the subsequent pregnancy increases infant protection.
Despite the high risk of Covid-19 in pregnant women and safety data regarding vaccines, only 71% of pregnant women in the United States are fully vaccinated as of May 14, 2022, significantly lower than for non-Hispanic black people. Women (58%).9 Recommendations from a health care provider have been found to be associated with a higher likelihood of maternal vaccination, and information about vaccine safety and infant protection through maternal vaccination has been shown to be important for a pregnant person’s decision-making process.10 Thus, this evidence that covid-19 vaccines can help protect infants and mothers is more relevant to patient counseling: a “two-in-one” agreement may encourage more mothers to get a covid-19 vaccine.