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The number of COVID-19 cases and deaths are rising again in some countries, apparently driven by the Omicron BA.4 and BA.5 subvariants. The European Centre For Disease Prevention And Control (ECDC) had recognized them as Variants Of Concern. The latest subvariants are believed to be more infectious than the past versions of Omicron., and capable of escaping immunity from a past infection or vaccination.
Meanwhile, the U.S. Centers for Disease Control and Prevention (CDC) is reminding people that COVID-19 vaccination (especially citing mRNA COVID-19 vaccines) remain the single most important tool to protect against serious illness caused by these the currently circulating variants.
In its latest Morbidity and Mortality Weekly Report (MMWR), the agency cited findings of a study which showed the effectiveness of 2, 3, and 4 doses of mRNA COVID-19 vaccines (Pfizer-BioNTech or Moderna) among adults with healthy immune systems during Omicron variant evolution in early 2022.
The CDC's MMWR highlighted the key findings of the new study, which examined data of thousands of emergency department/urgent care visits and hospitalizations with a COVID-19 like illness diagnosis from mid-December 2021 to mid-June 2022 in ten U.S. states. It found that
When Omicron BA.1 predominated, two doses of COVID-19 vaccines provided 61 per cent protection against COVID-19-associated hospitalizations. vaccine effectiveness increased to up to 92 per cent after a third dose.
During BA.2/BA.2.12.1 predominance, vaccine effectiveness against COVID-19-associated hospitalizations was 24 per cent with two doses and it increased to up to 69 per cent after a third dose. Among adults aged 50 years and older, vaccine effectiveness against COVID hospitalization increased to 80 per cent more than a week after the fourth dose.
However, the CDC indicated that a variant-specific vaccine may be recommended in the fall or winter.
Citing there has been increase in deaths and hospitalizations associated with the Omicron BA.5 variant, the agency urged people to stay up to date with recommended COVID-19 vaccinations. In the US, additional booster doses are recommended for people who are moderately to severely immunocompromised and adults over 50.