Fourth Covid-19 vaccine jab offers little more protection against Omicron


By AGENCY

More than half a million Israelis have now received a second booster dose against the SARS-CoV-2 virus, but it doesn’t appear to really increase protection against the Omicron variant. — dpa

Researchers in Israel, the first country in the world to offer people a fourth shot of Covid-19 vaccines, say this additional jab does not provide much additional protection against the SARS-CoV-2 Omicron viral variant.

“The rise in antibody levels that we saw with both Moderna and Pfizer (Covid-19 vaccines) are slightly higher than what we saw after the third booster vaccine,” said lead researcher and Tel Aviv’s Sheba Medical Center infectious disease unit director Dr Gili Regev-Yochay.

“But that good level is not enough for Omicron.”

Despite increased antibody levels, the fourth vaccine only offers a partial defence against the virus, she said on Jan 17 (2022).

According to her, breakthrough infections were also being observed in people who had been vaccinated four times.

She emphasised that the results were preliminary, and therefore, did not give more precise figures.

Around 150 participants in the study received a fourth dose of the Pfizer-BioNTech vaccine two weeks ago (early January 2022).

A week ago, another 120 participants received a fourth vaccination with the Moderna shot after three doses of the Pfizer-BioNTech vaccine.

This is the first trial worldwide studying a fourth vaccination with combined vaccines, Dr Regev-Yochay said.

The results of both groups after one week were very similar, she shared.

Covid-19 vaccines were developed to target a certain genetic sequence of the SARS-CoV-2 virus’ spike protein, which attaches to receptors on the surface of human cells.

However, experts say the Omicron variant’s spike protein is different in key places, making it harder for the immune system to recognise the virus.

Nevertheless, recent data from the UK Health Security Agency has shown that a third dose provides high levels of protection against severe illness from Omicron among older adults – a high-risk group.

Protection against hospitalisation among those aged 65 years and over remains at about 90% around three months after a booster jab.

However, protection against mild symptomatic infection drops to around 30% by about three months, according to the UK research.

Despite the limited success of a fourth jab, Israel’s decision to give the dose to immunocompromised people might have a small advantage, according to Dr Regev-Yochay.

However, she did not recommend extending this offer to the entire population.

People over 60 and medical personnel are also among those currently entitled to a fourth vaccination in Israel.

Dr Regev-Yochay spoke of a dilemma over whether to continue giving the fourth dose to healthy people over 60, given the early results of the study.

“If someone has a personal risk, then it is better to vaccinate now; if not, then maybe it is better to wait.”

Only about 62% of the 9.4 million Israelis are still considered fully vaccinated.

These are twice-vaccinated people up to six months after their second vaccination and people with booster vaccinations.

Thirty percent of the population have not been vaccinated at all, while the validity of their vaccination has expired for 8%.

Almost 4.4 million Israelis have already received their third vaccination dose, and more than 537,000 have already received their fourth, according to the Health Ministry. – dpa

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