COVID vaccine moderately protective against Omicron infection in kids

News brief

A South Korean study involving children aged 5 to 11 years estimates the vaccine effectiveness (VE) of two doses of the monovalent (single-strain) Pfizer/BioNTech COVID-19 vaccine against Omicron variant infection to be 58%, 50%, and 41% at 15, 31, and 61 days, respectively, with 100% protection against critical illness for up to 90 days.

Researchers from the Korea Disease Control and Prevention Agency published the study yesterday in JAMA Pediatrics. The team analyzed national COVID-19 surveillance data from 3,062,281 children aged 5 to 11 years from Mar 31 to Aug 6, 2022, when Omicron accounted for all sequenced cases in Korea.

Substantial protection against severe illness

By study end, 29,473 children (1.0%) had received two monovalent vaccine doses, while 3,016,913 were unvaccinated. Among the unvaccinated, 616,835 (182.6 per 100,000) tested positive for COVID-19, and 14 of those cases were critical (0.01/100,000). Among two-dose recipients, 1,867 (119.5/100,000) tested positive, but no cases were critical.

Estimated VE against infection after two vaccine doses was 57.6% (95% confidence interval [CI], 51.6% to 62.8%) at 15 to 30 days, 46.9% (95% CI, 43.7% to 49.9%) at 31 to 60 days, and 41.2% (95% CI, 34.3% to 47.4%) at 61 to 90 days. VE against critical infection was 100% (95% CI, 100% to 100%) at 90 days.

The authors noted that the study was conducted during a rapid rise in COVID-19 infections in Korean children. They also cautioned that the results may have been affected by the small number of critical infections.

"Other unmeasured bias might have occurred, including risk and behavioral differences between vaccinated and unvaccinated children," they wrote. "Further studies are needed about bivalent [two-strain] vaccine effectiveness because the present data are from a program using a monovalent vaccine."

The findings, the researchers said, reinforce previous research data showing that COVID-19 vaccination helps protect children against infection and serious illness. "COVID-19 vaccination, even with moderate effectiveness against all infection, can substantially prevent the risk of serious consequences of SARS-CoV-2 infection among children," they concluded.

Europe sees small but growing presence of COVID XBB.1.5 subvariant

News brief

In a statement today, the head of the World Health Organization (WHO) European office said data from countries in the region with strong genomic surveillance show a small but growing presence of XBB.1.5, the Omicron SARS-CoV-2 subvariant that has grown rapidly in the northeastern United States.

Hans Henri Kluge, MD, MPH, who directs the WHO's European office, said officials are working to assess the impact. He commended Denmark, France, Germany, and the United Kingdom for their genomic surveillance efforts, and he urged other countries to step up their own surveillance.

He said variant information submitted to the WHO and the European Centre for Disease Prevention and Control (ECDC) dropped dramatically between the beginning and the end of 2022. "Such a threat could come from a new variant of concern anywhere, anytime—including right here in Europe and central Asia," Kluge said.

The WHO European office agrees with the ECDC that China's surge isn't currently expected to significantly impact the COVID-19 epidemiologic picture in Europe. However, he said detailed and regular information from China, including local and variant information, is needed to better assess the evolving situation.

WHO to talk to Chinese officials

In a related development, at a WHO live social media Q and A session today, Mike Ryan, MD, who leads the WHO's health emergencies program, said WHO officials are slated to have follow-up talks tomorrow with Chinese health officials. And Maria Van Kerkhove, PhD, the WHO's technical lead for COVID-19, said the WHO will update its variant assessments tomorrow.

Meanwhile, WHO spokesperson Carla Drysdale told reporters at a briefing in Geneva today that the WHO's COVID-19 emergency committee will meet again on Jan 27, according to Reuters. WHO emergency committees typically meet every 3 months or more often as needed to discuss the latest developments and whether the situation still warrants a public health emergency of international concern. The group last met in mid-October.

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