Researchers in South Africa have published data in the New England Journal of Medicine (
link to study) showing that the two-dose Pfizer/BioNTech vaccine remains 70% effective against Covid-19 hospitalization, even in the face of the Omicron Variant. While Omicron has been found in several other studies to cause many more infections among the vaccinated and boosted (let alone the unvaccinated), these new findings indicate that the implications of these infections remain far less dire than they were during the pre-vaccine era. In other words, the vaccines have held up to their greatest challenge yet. As expected, a majority of Omicron Covid-19 hospitalizations in South Africa occurred among the unvaccinated.
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Some data that were not published—but which were shared with Inside Medicine by the research team that published this latest study from South Africa—show an important age-specific pattern: among individuals ages 18-29, vaccine effectiveness against Omicron hospitalization was found to be 92%. Among individuals ages 30-39, 40-49, 50-59 vaccine effectiveness was somewhat lower but still highly impressive, at 75%, 82%, and 74% respectively. However, vaccine effectiveness against Omicron-related hospitalization was another notch lower in older groups, with vaccine effectiveness pegged at 67% among individuals ages 60-69 and 59% among those ages 70-79 (Data for 80+ were not specified).
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Lower vaccine effectiveness against Omicron in older populations is cause for concern. These findings clearly suggest, yet again, that booster doses for people in older age groups (and other high-risk groups such as those with immune compromise) stand to improve outcomes meaningfully. That also means that outcomes in the United States may be better than elsewhere, since around 57% of the fully vaccinated US population ages 65 and older have already been boosted. Just how much added protection against severe disease and hospitalization those booster doses provide on top of these new figures from South Africa remains undetermined. But again, the effects will likely be age-dependent, with the most benefit coming to those who are the most vulnerable.