The mRNA COVID-19 Boosters Protect Against XBB and XBB15

The CDC is reporting the bivalent mRNA (Pfizer-BioNTech, and Moderna) boosters provided protection against symptomatic COVID-19 infection of the XBB and XBB15 variants for at least 3 months in individuals who received 2-4 monovalent vaccine doses.

"Among 29,175 nucleic acid amplification tests (NAATs) with spike gene (S-gene) amplification (SGTF) or S-gene target presence (SGTP) results available from adults who had previously received 2–4 monovalent COVID-19 vaccine doses, the relative VE of a bivalent booster dose given 2–3 months earlier compared with no bivalent booster in persons aged 18–49 years was 52% against symptomatic BA.5 infection and 48% against symptomatic XBB/XBB.1.5 infection.

The results of this analysis was published in the latest Morbidity and Mortality Weekly Report.

VE was consistent amongst different age cohorts with some drop off in the older groups. “VE against symptomatic XBB/XBB15-related infection was 49% among persons aged 18–49, 40% among persons aged 50–64 years, and 43% among those aged ≥65 years,” the investigators wrote in the MMWR.

"Today we have additional evidence to show that these updated vaccines are protecting people against the latest COVID-19 variants," Brendan Jackson, MD, MPH, CDR, head of CDC’s COVID-19 response, said in a media briefing yesterday.

According to the authors, data was collected from the Increasing Community Access to Testing (ICATT) national pharmacy program for SARS-CoV-2 testing and analyzed to estimate VE of updated (bivalent) mRNA COVID-19 vaccines against symptomatic infection caused by BA5-related and XBB/XBB15-related sublineages among immunocompetent adults from December 1, 2022–January 13, 2023.

In addition to the aforementioned findings, the investigators said the booster protection may show signs of lasting longer than 3 months. “Evidence of waning VE by 2–3 months after receiving a bivalent dose based on point estimates was minimal, although estimates were imprecise. Sensitivity analyses did not show a meaningful change in VE by different analytic period start dates,” the authors wrote.

This type of data reported by CDC could be significant going forward. The latest FDA VRBPAC meeting is happening today and the committee is convening to discuss how COVID-19 vaccines will be offered going forward. Ahead of the meeting, the FDA presented a plan looking at distributing COVID-19 vaccines annually in the fall like influenza vaccines are scheduled. This would be a departure from the current vaccine distribution where people needed to be updated periodically. If the boosters' VE lasts three months or more, it could potentially provide coverage for people if they get the vaccines in the fall through most of the winter months before they became vulnerable to COVID-19 in the late winter/early spring.

Check back with Contagion later this afternoon for the news coverage on the VRBPAC meeting.