Two doses of vaccines cannot fully against Omicron

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In a new study from the University of Hong Kong, researchers found that most individuals after being given two doses of the vaccine (either BioNtech or Coronavac) do not produce sufficient levels of serum antibodies against the new Omicron virus variant.

The public is advised to get a third dose of the vaccine as soon as possible while waiting for the next generation of the more matched vaccines.

The SARS-CoV-2 Omicron variant, first identified in November 2021, is spreading worldwide.

This variant is particularly worrisome due to a large number of mutations in the virus that could affect infectivity or vaccine efficacy.

To assess the effectiveness of existing COVID-19 vaccines in Hong Kong against this novel variant, the team tested the ability of serum samples from fully vaccinated recipients to neutralize this variant.

Serum neutralizing antibody titers are currently the only easily reproducible surrogate marker of protection against COVID-19.

To test the ability of vaccine recipients’ serum antibodies to neutralize the Omicron variant, the team used sera from two groups of vaccine recipients who have received two doses of BNT162b2 (BioNtech) or Coronavac. Each group consists of 25 people.

The study aims to more fully evaluate the health risk of the Omicron variant to the Hong Kong population and the need for a universal third dose.

Two Omicron variants present in Hong Kong were tested, one from South Africa and the other from Nigeria (with the additional R346K mutation).

The ability of serum antibodies to neutralize the Alpha, Beta, and Delta strains was also tested as a control.

The team found only five out of 25 Biontech vaccine recipients had neutralizing ability against the Omicron variant virus, and the vaccine efficiency was significantly reduced to 20—24%.

Compared to the original SARS-CoV-2 strain, the titer of neutralizing antibodies against the Omicron variant has decreased by 36—40 fold.

None of the serum of the 25 Coronavac vaccine recipients contains sufficient antibodies to neutralize the Omicron variant at the limit of 1 in 10 dilutions.

The team says the Omicron variant virus was able to reduce the effectiveness of two doses of the COVID-19 vaccine, particularly against Coronavac.

Therefore, COVID-19 vaccine recipients or even those recovered COVID-19 patients may be at a higher risk of breakthrough or reinfection.

The third dose of the COVID-19 vaccine is needed to enhance the antibody response against the Omicron variant.

If you care about Omicron, please read studies about drug combo that can effectively fight COVID-19, and everything you need to know about Omicron and COVID boosters.

For more information about health, please see recent studies about people with COVID-19 who recover faster with this treatment, and results showing Omicron may not be the final variant, but it may be the final variant of concern

The study is published in Clinical Infectious Diseases.

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