Two vaccine doses not enough for Omicron

Three doses of the Pfizer vaccine offer protection equivalent to two doses against other variants, new research has found.

The study from Germany published in the journal Science used sera from 51 participants, which was challenged with Wuhan, Beta, Delta, or Omicron variants to check for antibody levels. The participants had received either two or three doses of the Pfizer vaccine. Though neutralising antibodies are just one measure of vaccine effectiveness, the authors said they can be strongly predictive of the degree of immune protection against symptomatic COVID-19 infection.

After 21 days, the effectiveness of a double dose had waned significantly against Omicron, with 20 out of 32 immune sera displaying no detectable neutralizing activity against Omicron. But within 4 weeks of a third dose, the protective effect against Omicron had increased 23-fold compared with two doses.

“Our data show that a third BNT162b2 [Pfizer] dose effectively neutralizes Omicron at a similar order of magnitude as was observed after two doses of BNT162b2 against wild-type SARS-CoV-2,” the authors concluded.
Read more: Alexander Muik et al. Neutralization of SARS-CoV-2 Omicron by BNT162b2 mRNA vaccine–elicited human sera, [Full article] Science, first release 18 Jan 2022. DOI: 10.1126/science.abn7591 Cidrap news updateSource: Risks 1029 

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