Maternal SARS-CoV-2 vaccination and protection of infants against SARS-CoV-2 during the first 6 months of life

Descriptive statistics and characteristics

We identified 62,117 infants born between December 15, 2020 and May 31, 2022 at Kaiser Permanente Northern California (KPNC), an integrated care delivery organization. Of these infants, 21,891 (35.2%) were excluded based on maternal exclusion criteria and 10,412 (16.8%) were excluded after applying infant exclusion criteria for the main analysis (Fig. 1). The final study population included 30,311 (48.8%) of her infants who were KPNC members at least 2 months of age. Her mean age at pregnancy onset was 31.62 years (standard deviation 4.66 years). Most mothers (66.14%) were between the ages of 25 and 35, more than a quarter (27.27%) were Asian, 5.16% were black, 24.44% were Hispanic, and 37.57% were white. Of the infants in the cohort, 19,418 (64.06%) mothers were not vaccinated during pregnancy, 1,138 (3.75%) mothers received one dose of mRNA COVID-19 vaccine, and 9,755 (32.18%) mothers received one dose of mRNA COVID-19 vaccine. %) were vaccinated more than once during pregnancy. (table 1). Most of the single-vaccinated mothers (1,032 of 1,138) received the vaccine in the third trimester.

Children born between December 15, 2020 and May 31, 2022 in Kaiser Permanente Northern California.

During the first 6 months of life, 940 (3.10%) infants tested positive for SARS-CoV-2 by polymerase chain reaction (PCR) and 10 (0.03%) infants tested positive for SARS-CoV-2. I tested positive and was hospitalized.

Vaccine efficacy: a primary design cohort analysis

In the delta-dominant period, infants whose mothers received at least two doses of mRNA vaccine for COVID-19 during pregnancy had a lower gross incidence of SARS-CoV-2 positivity at 2, 4, and 6 months of age ( 0.75, 1.43, and 1.56 infants per 100 person-years [PY], respectively) than those whose mothers had not been vaccinated during pregnancy (5.47, 5.10, and 4.78 infants per 100 PY, respectively).After adjusting for covariates, vaccination during pregnancy significantly reduced the risk of testing an infant positive for SARS-CoV-2 by 84% (95% confidence interval) [CI]66, 93) at 2 months, 62% at 4 months (95% CI: 39, 77), 56% at 6 months (95% CI: 34,71) . The efficacy of one vaccination was 68% (95% CI: 12, 88) (Table 2). During the Omicron dominance period, two or more doses during pregnancy reduced the risk of an infant testing positive for SARS-CoV-2 by 21% (95% CI: -21, 48) at 2 months of age. , 14% (95% CI at 4 months of age: -8, 32), 13% at 6 months of age (95% CI: -3, 26) (Table 2).All these results were similar to those without covariate adjustment (Supplementary Table 1).

In a trimester-by-trim supplemental analysis of vaccination, a second dose in the second and third trimesters increased the risk of an infant testing positive for SARS-CoV-2 during the delta-dominant period by 91% (95% CI: 63, 98) and 85 decreased. % (95% CI: 50, 96) for the first 2 months, respectively, 59% (95% CI: 21, 79) and 67% (95% CI: 37, 83) for the first 4 months and 67% (95% CI: 37, 83) for the first 6 months 64% (95% CI: 31, 81) and 53% (95% CI: 24, 71).In the delta stage, one dose in the third trimester reduced the risk of an infant testing positive for SARS-CoV-2 at 6 months of age by 74% (95% CI: 19, 92) (table 3).A similar pattern was observed for vaccine efficacy up to trimester in the Omicron-dominant period, but estimates of vaccine efficacy up to trimester were imprecise and much lower than in delta (Table 1). 3).

Over the study period, the gross rate of hospitalization for positive SARS-CoV-2 testing was lower at 6 months of age in infants whose mothers had received at least two doses of COVID-19 mRNA vaccine during pregnancy. Mothers were not vaccinated during pregnancy (21/100,000 PY vs. 100/100,000 PY). Her VE for hospitalization was not estimated due to the very small number of hospitalized cases.Only one child was hospitalized for a vaccinated mother, and she was the nine hospitalized child for an unvaccinated mother (Table 1). 1).

Secondary Analysis Results Using Test Negative Design (TND)

In TND, at least one maternal vaccination during the Delta predominance period was associated with a 95% (95% CI: 76, 99) estimated to have decreased. , 70% (95% CI: 52, 82) at 4 months of age and 61% (95% CI: 42, 74) at 6 months of age (Supplementary Table 2). During the Omicron preponderance period, maternal vaccination with at least two doses reduced the risk of an infant testing positive for SARS-CoV-2 by 43% (95% CI: -4, 69) in the first two months of life. ), decreased by 36% (95 % CI: 11, 55 at 4 months of age) and 41% (95% CI: 25, 53) at 6 months of age (Supplementary Table) 2).The results were unchanged when no covariate adjustments were made (Supplementary Table 3).

Additional supplemental analysis

Among children whose mothers received 1 dose before and 1 dose during pregnancy during the omicron period, VE against infection was 46% (95% CI: -23, 77) at 2 months of age and 46% (95% CI: -23, 77) at 2 months of age 16% (95% CI: -28, 50) at 4 months (95% CI: -32, 36) compared with children whose mothers had not been vaccinated, 3% (95% CI: -32, 36) at 6 months 3% (95% CI: -32, 36) Four). For children whose mother received one dose before and two doses during pregnancy, her VE against infection was 89% at 2 months of age, 73% at 4 months of age, and 73% at 6 months of age. was 48%.