A Covid booster dose boosts vaccine effectiveness against Omicron by 88%, according to a study
Despite the fact that the Omicron variant of Covid has been shown to evade vaccines, two new studies led by the UK health agency found that a third booster dose increases vaccine effectiveness by 88%.
The studies, led by the UK Health Security Agency (UKHSA), discovered a significant reduction in the risk of hospitalization for Omicron cases after three doses of vaccine compared to unvaccinated people.
The first study found that when compared to unvaccinated Omicron cases, the risk of hospitalization is 81% lower after three doses.
Previous research has found that Omicron’s vaccine effectiveness against the symptomatic disease remains lower than Delta’s, with waning by 10 weeks after the third dose.
The researchers linked symptomatic cases to hospitalization data in the second study.
They discovered that after three doses of vaccine, the risk of hospitalization for an asymptomatic case of Omicron identified through community testing was reduced by 68 percent when compared to similar individuals with Omicron who were not vaccinated.
However, when combined with the protection against becoming a symptomatic case, this results in an 88 percent vaccine effectiveness against hospitalization for Omicron after three doses of vaccine, according to the study.
“That’s a big boost of protection for third dose vaccine vs hospitalization from Omicron infection,” Eric Topol, a physician-scientist and professor of molecular medicine at Scripps Research, said in a tweet.
“Vaccine efficacy increased from 52% (due to 2-dose waning after 6 months) to 88 percent after the third dose,” he added.
Although the effectiveness against symptomatic disease is waning, there is insufficient data to assess the duration of protection against hospitalization, which is expected to last longer, according to the researcher.
The study also found that booster doses were less effective for Omicron than for Delta. There was no effect against Omicron 20 weeks after the second dose in those who had received two doses of AstraZeneca.
Among those who had received two doses of Pfizer or Moderna, effectiveness dropped from around 65 to 70% to around 10% 20 weeks after the second dose.
Vaccine effectiveness ranged from 65 to 75 percent two to four weeks after a booster dose, dropping to 55 to 70 percent five to nine weeks later, and 40 to 50 percent ten weeks or more later, according to the studies.
“These estimates suggest that vaccine effectiveness against symptomatic disease with the Omicron variant is significantly lower than with the Delta variant and wanes rapidly,” according to the UKHSA.
“However, protection against hospitalisation is much greater than protection against symptomatic disease, particularly after a booster dose, where vaccine effectiveness against hospitalisation is close to 90%,” they added.
