Bivalent mRNA vaccine confers protection against SARS-COV-2 infection in young children

Bivalent COVID-19 vaccine conferred protection against SARS-COV-2 infection among children and adolescents aged 5–11 years, according to a recent study presented at IDWeek 2023.

The bivalent mRNA COVID-19 vaccine booster dose, composed of mRNA from ancestral and Omicron BA.4/BA.5 strains, was recommended for adolescents aged ≥12 years on September 1, 2022 and for children aged 5–11 years on October 12, 2022, said study author Dr Leora Feldstein from Centers for Disease Control and Prevention in Atlanta, Georgia, US.

“However, data demonstrating the effectiveness of bivalent boosters among children and adolescents are still limited,” she noted.

Using data from three community cohort studies (CASCADIA, CoVE, and PROTECT), the researchers identified 2,959 children and adolescents (median age 10.6 years, 48 percent female) to assess the vaccine effectiveness (VE) of the bivalent COVID-19 in this study population. Of these, 752 participants received bivalent vaccine dose during the study period (from September 4, 2022 to January 31, 2023). [IDWeek 2023, abstract 2082]

Of the 426 participants who were SARS-CoV-2 positive, 238 of whom were infected with the Omicron BA.4/BA.5 variants, which accounted for the majority of infections during the study period.

Vaccine effectiveness

Compared with participants who were unvaccinated or who received a monovalent dose only, overall adjusted VE against infection was 54 percent among those who received a bivalent dose.

When stratified by age, adjusted VE of a bivalent dose did not differ between the younger cohort (aged 5–11 years) at 59 percent and older cohort (aged 12–17 years) at 48 percent.

Similar patterns of VE were observed regardless of the timing of receipt of the bivalent dose, within 7–60 days (51 percent) and 61–150 days (62 percent), as well as when restricted to symptomatic illness (49 percent).

Taken together, “children and adolescents aged 5–11 years with a bivalent dose were less likely to be infected with SARS-CoV-2 than those who were unvaccinated or who received a monovalent dose [only],” said Feldstein.

These findings were consistent with those of the only other study that estimated bivalent VE against infection among children aged 5–11 years, showing that VE against infection was 47 percent at 2 months after receipt of a bivalent dose, Feldstein noted.

“Our study showed that from September 2022 to January 2023, which included the period of Omicron BA.4/BA.5 predominance, the bivalent COVID-19 vaccine … reduced the risk of SARS-CoV-2 infection and symptomatic illness among children and adolescents,” said Feldstein.

“Our results support current guidelines that all children and adolescents should stay up to date on their COVID-19 vaccination,” she added.