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”.
In addition, around the same percentage of hospital workers who received the fourth dose caught the virus as those who didn’t get the fourth booster.
With the UKHSA reporting three-dose protection against Omicron at under 50% after 10 weeks, this suggests a limit to what repeated shots of the same vaccine can achieve.
The findings come as Israel experiences a large surge in reported infections and ICU admissions, despite 65% of the country being at least double-dosed, 46% being triple-dosed, and some even quadruple-dosed. It will be interesting to see how this translates into deaths (how many of them are incidental admissions?), and what this might tell us about Omicron and vaccines.


To join in with the discussion please make a donation to The Daily Sceptic.
Profanity and abuse will be removed and may lead to a permanent ban.