4th shot of COVID-19 vaccine less effective against Omicron
Israel's Sheba Medical Center has given second booster shots in a trial among its staff and is studying the effect of the Pfizer booster in 154 people after two weeks and the Moderna booster in 120 people after one week, said Gili Regev-Yochay, director of the Infectious Diseases Unit, Reuters reported.
These were compared to a control group that did not receive the fourth shot. Those in the Moderna group had previously received three shots of Pfizer's vaccine, the hospital said.
The vaccines led to a increase in the number of antibodies "even a little bit higher than what we had after the third dose", said Regev-Yochay.
Yet, this is probably not enough for the Omicron. We know by now that the level of antibodies needed to protect and not to got infected from Omicron is probably too high for the vaccine, even if it's a good vaccine,
she told reporters.
The findings, which the hospital said were the first of its kind in the world, were preliminary and not yet published.
Citing preliminary findings of a study by Sheba Medical Center, Israeli Prime Minister Naftali Bennett said on 4 January that
- „a week into the fourth dose, we know to a higher degree of certainty that the fourth dose is safe;
- we know that a week after administration of a fourth dose, we see a five-fold increase in the number of antibodies in the vaccinated person;
- this most likely means a significant increase against infection and ... hospitalisation and (severe) symptoms.”
Israel has played a leading role in studying the effects of COVID-19 vaccines, as the fastest country to roll out two-dose inoculations to a wide population a year ago and one of the first to give third shots as boosters.
It is now administering fourth doses to people over 60, health workers and immunocompromised patients.
More than 537,000 Israelis have received a fourth dose of vaccine, according to the health ministry's latest figures.
More than 80% of Israel's adult residents have received two coronavirus vaccine shots and more than half have also been given a booster. The corresponding ratios in Hungary are 62% and 35%. Hungary had 4,210 Covid deaths per one million population (4th highest figure in the world), versus 892 in Israel (89th).
It is important to note that while studies suggest that a 3rd dose does not protect against Omicron sufficiently, practical experience shows that it is mostly unvaccinated people that are hospitalised with Omicron, which causes a milder course of disease overall, at an even higher rate than with the Delta variant.
Cover photo: MTI/Attila Balázs