In a recent study under review on the Nature Portfolio journal and currently posted to Research Square* preprint server, researchers evaluated the efficacy of maternal coronavirus disease 2019 (COVID-19) vaccination against infection of infants with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

The US (US) has recorded greater than 15 million pediatric COVID-19 cases until September 2022, and pediatric patients account for about 18% of US COVID-19 cases. Notably, through the Omicron wave, children younger than six months accounted for 44% of the general COVID-19-associated hospitalizations amongst those under 4.

SARS-CoV-2 vaccines have been effective, particularly against the Delta variant. Nevertheless, they were less effective against SARS-CoV-2 Omicron. Since infants younger than six months are ineligible for COVID-19 vaccination, they’re reliant on the immunity acquired placentally from their moms.

Nevertheless, vaccination while pregnant is believed to guard infants against SARS-CoV-2. As well as, recent studies reported that maternal vaccination was linked to a lower risk of infection and hospitalization in infants of their first 4 and five months.  

​​​​​​​Study: Maternal SARS-CoV-2 Vaccination and Infant Protection Against SARS-CoV-2 Through the First 6 Months of Life. ​​​​​​​Image Credit: Marina Demidiuk / Shutterstock

In regards to the study

In the current study, researchers assessed the effectiveness of COVID-19 mRNA vaccination while pregnant against infection of infants with SARS-CoV-2. The study was conducted on infants born from December 15, 2020, to May 31, 2022, at Kaiser Permanente Northern California (KPNC), an integrated healthcare delivery organization providing comprehensive access to healthcare to members.  

Infants were excluded in the event that they didn’t turn into KPNC members inside two months of birth or were born to moms who 1) didn’t have primary KPNC facility project, 2) weren’t 16-50 years old, 3) tested SARS-CoV-2-positive before pregnancy, 4) had anti-SARS-CoV-2 antibodies before pregnancy, 5) were vaccinated before pregnancy, 6) received vaccines apart from mRNA vaccines, and seven) weren’t continuous members of KPNC.

The study’s outcomes were the primary positive SARS-CoV-2 polymerase chain response (PCR) test result and hospitalization of infants inside six months of life. As well as, electronic health records (EHRs) of moms were accessed to acquire information on covariates equivalent to age, race/ethnicity, the first KPNC facility, neighborhood deprivation index (NDI), insurance payor, pre-pregnancy body mass index (BMI), diabetes status, hypertension, and parity.

The authors used Cox proportional hazards to compute the hazard ratio of SARS-CoV-2 infection between infants born to vaccinated and non-vaccinated moms. Infants were followed up from birth to their first positive test. Moreover, secondary analyses, implemented as a test-negative design, were conducted by restricting the population to infants tested for SARS-CoV-2 no less than once. 

Findings

The researchers identified greater than 62,000 infants born at KPNC facilities; after exclusions, 30,288 infants were included for evaluation. Most moms (66.15%) were aged 25 – 35 years and White (37.57%), followed by Asians (27.26), Hispanics (24.45%), and Black (5.16%). Moms of 19,179 infants (63.32%) weren’t vaccinated while pregnant; 3.42% of moms received one dose of mRNA vaccine, 31.22% received two doses, and a pair of% received three doses while pregnant.

In the primary six months of life, 3.1% of infants tested SARS-CoV-2-positive, and 10 needed to hospitalize. The crude incidence of SARS-CoV-2 test positivity was lower amongst infants born to double-vaccinated moms than those with non-vaccinated moms through the Delta wave. After adjusting for covariates, maternal vaccination while pregnant was significantly related to a lower risk of infants testing positive by 85% and 57% through the first two and 6 months (of life), respectively.

Through the Omicron wave, maternal vaccination decreased the danger of infants testing positive by 22% and 12% in the primary two and 6 months, respectively. The general crude hospitalization rate of infants of their first six months was low for those born to double-vaccinated moms.

Just one infant of a vaccinated mother was hospitalized, while the remaining (hospitalized) infants had non-vaccinated moms. Secondary evaluation indicated that maternal vaccination reduced infant test positivity by 63% and 40% in the primary six months of life, during Delta and Omicron waves, respectively.

Conclusions

In summary, the researchers observed that two mRNA vaccine doses administered while pregnant were related to a reduced risk of infants testing positive for SARS-CoV-2 of their first six months. Protection declined with the age of infants. Maternal vaccination was less effective through the Omicron period. Although vaccination efficacy against infant hospitalization was not assessed because of the small sample, moms of nine hospitalized infants weren’t vaccinated, suggesting that maternal vaccination may protect infants from hospitalization.

*Vital notice

Research Square publishes preliminary scientific reports that will not be peer-reviewed and, due to this fact, mustn’t be thought to be conclusive, guide clinical practice/health-related behavior, or treated as established information.