In a recent study published in The New England Journal of Medicine, researchers evaluated the effectiveness of maternal messenger ribonucleic acid (mRNA) vaccines during pregnancy against hospitalization for coronavirus disease 2019 (COVID-19 ) in infants younger than 6 months.
Study: Maternal vaccination and risk of hospitalization for Covid-19 in infants. Image credit: BaLL LunLa / Shutterstock
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Babies under six months of age are at increased risk for complications from severe acute respiratory syndrome from coronavirus 2 (SARS-CoV-2) and are not eligible for COVID-19 vaccines. Transplacental transfers of maternal anti-SARS-CoV-2 antibodies after vaccination of mothers against SARS-CoV-2 could confer immune protection to their infants against SARS-CoV-2.
The authors of the present study previously reported that the risk of hospitalization associated with COVID-19 was 61% lower among infants under 6 months of age born to mothers who had received double vaccination (mRNA) during pregnancy when SARS -CoV-2 Delta (B.1.617.2) was dominant.
About the study
In the present case-control study, the researchers expanded their previous analysis by exploring the protective role of mRNA vaccination of pregnant women against COVID-19-associated hospitalization in infants less than 6 months of age. SARS-CoV-2 Omicron (B). .1.1.259) variant. Compared to their previous study, the present study comprised a much larger sample size, i.e., more than 361 and 309 infant cases and control infants, respectively.
The study was conducted between July 1, 2021 and March 8, 2022 and included infants with hospitalizations associated with COVID-19 (case infants) and infants without hospitalizations associated with COVID-19 (infants control) in 30 pediatric hospitals in 22 states. Case infants were identified using active continuous surveillance data from disease control and prevention centers (CDCs) funded by overcoming the COVID-19 network.
Data were obtained on demographic parameters, history of COVID-19, and clinical findings of existing disease using electronic medical records and interviewing the parents (or guardians) of the infants. Information on maternal vaccination was obtained, such as vaccination dates, doses received, whether mothers were vaccinated during pregnancy, where mothers were vaccinated, vaccine manufacturers, and card availability. of vaccination against COVID-19.
Data were also obtained on COVID-19-associated hospitalizations, admissions to intensive care units (ICUs), and critical cases of COVID-19 that require life-support interventions or that resulted in death. Life support interventions included noninvasive mechanical ventilation (continuous or positive airway pressure), invasive mechanical ventilation, vasoactive infusions, and extracorporeal membrane oxygenation.
All case infants were diagnosed as SARS-CoV-2 positive by antigen testing or reverse transcription polymerase chain reaction (RT-PCR) within ten days of the onset of symptoms or three days of hospitalization. Mothers were considered fully vaccinated if they had received double doses of mRNA-1273 or BNT162b2 mRNA vaccines.
Women who received the initial dose of the vaccine before pregnancy and the second dose of the vaccine after pregnancy were included in the analysis. Because protective immunity is built up after approximately two weeks of vaccination, infants born to vaccinated mothers <14 days before delivery were excluded from the analysis.
In addition, infants born to mothers who had received a triple mRNA vaccine (n = 29 infants) or who were vaccinated with the Ad26.COV2.S mRNA vaccine (n = 13 infants) due to small number of pregnant women in these two categories. The efficacy of the vaccine was estimated by comparing the probabilities of COVID-19 severity outcomes in both groups of infants born to fully vaccinated mothers during pregnancy in the Delta predominant periods (between 1 July). 2021 and December 18, 2021) and the predominance of Omicron (between December 19 and 2021). March 8, 2022).
Results
The analysis was performed for 537 and 512 infant cases and control infants, respectively. Among the babies in the cases, 181 infants were hospitalized with Delta infections and 356 infants were hospitalized with Omicron infections. The mean age of the study participants was two months. About 16% and 29% of infant cases and control infants, respectively, were born of fully vaccinated women during pregnancy.
Compared with the cases of babies born to mothers who were not fully vaccinated during pregnancy (n = 450 infants), the infants of cases born to women fully vaccinated during pregnancy (n = 87 infants) showed income in the Lower ICUs (23% versus 13%). In addition, infants demonstrated lower critical SARS-CoV-2 infection (12% versus 9%), invasive mechanical ventilation requirements (7% versus 3%), noninvasive mechanical ventilation requirements (8% versus 6%). %) and vasoactive. Infusion requirements (3% versus 1%) compared to control infants.
Among infant cases, 21% (n = 113) were admitted to the ICU, of which 12% (n = 64) received vasoactive infusions or mechanical ventilation. Two case babies were reported to die from COVID-19, and two case babies required extracorporeal membrane oxygen supplements, none of whose mothers received double mRNA vaccination while they were pregnant.
The efficacy of complete maternal mRNA vaccines against COVID-19-associated hospitalization in infants was reported to be 52%, with 80% efficacy during the predominance of Delta and 38% efficacy. during the predominance of Omicron. The efficacy was 70% against admission to the ICU associated with COVID-19 and 47% against hospitalization that did not require admission to the ICU. In addition, the efficacy was 38% and 69% when mothers were vaccinated during the initial 20 weeks of gestation and after 20 weeks of gestation, respectively.
Overall, the study findings showed that full (double dose) vaccination of maternal mRNA reduced the risk of COVID-19-associated hospitalizations among infants less than 6 months of age.