COVID-19 vaccine effective against hospitalization from Omicron variant

The BNT162b2 vaccine is moderately effective at preventing hospitalization from the Omicron strand of COVID-19 for 4 months after vaccination in pediatric patients aged 5 to 11 years, according to a recent study.

The COVID-19 vaccine had a 90.7% vaccine effectiveness (VE) against early strands of the virus in children, but the significant immune evasion of the Omicron variant has had a major impact on the VE. While early data indicated a VE of 31% against Omicron infection and 68% to 74% against hospitalization, there is little data on VE against Omicron after 2 months.

To determine VE against Omicron over time in children aged 5 to 11 years, investigators gathered real-world evidence from community-dwelling children aged 5 to 11 years with COVID-19 symptoms or positive polymerase chain reaction (RT-PCR) from January 2 to August 27, 2022. 

In cases of multiple positive tests, the first was used for the analysis. Exclusion criteria included being asymptomatic during testing, having symptoms unrelated to COVID-19, and having no information on symptoms during testing. A control group comprised of children with a negative COVID-19 RT-PCR test.

Data was gathered on COVID-19 vaccine status, vaccine product, dose administered, dose number, date of administration, and dosing info. Hospitalization and death were defined as severe outcomes which could be attributed to COVID-19. 

Covariates included sex, age, and postal code. Influenza was recorded as a comorbidity, with receipt of influenza vaccination obtained from physician and pharmacist billing claims.

There were 114,637 children aged 5 to 11 years with COVID-19 RT-PCR testing recorded during the testing period, 14,673 of which were included in the analysis. Of these, 45.4% were positive and 54.6% negative.

Positive cases were more often seen in children who were older, had more people dwelling in residing area, and were less likely to be vaccinated against COVID-19, have a positive COVID-19 test more than 90 days after the index date, have received prior influenza vaccination, and be the child of a healthcare worker. 

Children with negative tests had a longer mean dosing interval between 2 doses than those with positive tests. Also, vaccinated children were more often older, residing in the highest neighborhood income quartile, had received prior influenza vaccination, not reside in lower income areas, and were the child of a healthcare worker.

VE against infection was 9% 14 days or more after the first dose and 49% 7 days or more after the second dose. The peak VE was 24%, declining over time after each dose. Children with longer dosing intervals had a higher VE, with a VE of 57% seen in children with a dosing interval of 56 days or more and a VE of 12% in children with an interval of 15 to 27 days.

Investigators found 138 cases of hospitalization or death, 5 or less of which were death. Severe COVID-19 was more often seen in older patients, patients residing in lower income areas, patients with comorbidities, and patients less likely to be vaccinated against COVID-19, have received prior influenza vaccination, and be the child of a healthcare worker.

Severe COVID-19 was more often seen in unvaccinated children, with a VE of 79% against severe outcomes recorded 7 or more days after a second dose. This showed moderate VE after 2 doses, which waned over time after each dose.

Reference

Piché-Renaud P, Swayze S, Buchan SA, et al. COVID-19 vaccine effectiveness against omicron infection and hospitalization. Pediatrics. doi:10.1542/peds.2022-059513