Data show benefits of additional vaccine doses against omicron
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A third or fourth dose of one of the COVID-19 messenger RNA vaccines offered increased protection among adults during the early omicron wave, according to data from more than 270,000 patients reported Friday in MMWR.
“The findings of this study, in conjunction with recently published data [in The New England Journal of Medicine] showing people infected with BA.2 may also have antibodies that can protect against illness with BA.5, suggest that currently available vaccines may provide protection against serious illness caused by the currently circulating BA.5 variant,” the CDC said in a press statement announcing the study.
White House COVID-19 advisors acknowledged this week that second booster doses may soon be available to all adults to combat the BA.4 and BA.5 omicron subvariants. BA.5 and BA.4 account for 65% and 16% of new infections, respectively.
Ruth Link-Gelles, PhD, an epidemiologist with the CDC’s COVID-19 Emergency Response Team, and colleagues assessed the effectiveness of second, third and fourth doses of the Pfizer-BioNTech or Moderna COVID-19 vaccines among adults with healthy immune systems using VISION Network data on more than 214,000 ED and urgent care visits and more than 58,000 hospitalizations associated with a COVID-19-like illness diagnosis. The data were from 10 U.S. states between mid-December 2021 and mid-June 2022.
Overall, the study revealed that when BA.1 was the predominant variant, VE for two doses was 61% against COVID-19-associated hospitalizations but increased to between 85% and 92% after receipt of a third or booster dose.
After BA.2/BA.2.12.1 became predominant, vaccine effectiveness (VE) for two doses was 24% against COVID-19-associated hospitalizations and increased to 52% to 69% after a third dose. According to the study, similar trends were seen among ED and urgent care encounters, with lower VE during BA.2/BA.2.12.1 prevalence and higher VE with three or four doses compared with the initial two dose series.
Additional data showed that VE against COVID-19-associated hospitalization among adults aged 50 years or older — for whom second boosters are authorized — during BA.2/BA.2.12.1 was 55% more than 4 months after a booster dose and increased to 80% more than a week after the fourth dose.
“Immunocompetent persons should receive recommended COVID-19 booster doses to prevent moderate to severe COVID-19, including a first booster dose for all eligible persons and second dose for adults aged 50 years or older at least 4 months after an initial booster dose,” the authors wrote. “Booster doses should be obtained immediately when persons become eligible.”
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