A fourth dose of Covid mRNA vaccine is not effective against Omicron infection, preliminary research from Israel has shown. Health Policy Watch has more.
“Despite a significant increase in antibodies after the fourth vaccine, this protection is only partially effective against the Omicron strain, which is relatively resistant to the vaccine,” lead researcher Prof Gili Regev-Yochay, told a media briefing on Monday.
Some 154 health workers at Sheba Medical Center received their fourth Pfizer shot two weeks ago. A week ago, 120 health workers received a shot of Moderna following three doses of Pfizer one week ago.
They were matched with a control group of around 6,000 health workers who have been being followed by the hospital since the start of Israel’s vaccination campaign in December 2020.
According to Regev-Yochay, the third dose resulted in “much higher antibodies, neutralisation and the antibodies were not just higher in quantity but also in quality” than the second dose – but the fourth vaccine did not show significant antibody increase.
“Maybe there are a few more antibodies but not much more compared to the third dose,” said Regev-Yochay.
Last week, she told Israeli Prime Minister Naftali Bennett that there had been a five-fold increase in antibodies in people who took the fourth dose, but she later told a radio station that “the amount of antibodies returns to the level it was after the third vaccine, not more. It’s nice, but it’s not what we expect from a booster”.