- Three vaccine doses are likely to provide sufficient long-term protection against severe Covid-19, a prominent Israeli doctor has said.
- Professor Eyal Leshem, an infectious disease specialist at Israel's Sheba Medical Center, also said vaccines may need to be tailored to new variants every few years.
- Israel began to roll out fourth vaccine doses at the end of last year for older adults, some healthcare workers and people with weakened immune systems.
Three vaccine doses are likely to provide sufficient long-term protection against severe Covid-19, a prominent Israeli doctor has said.
Speaking to CNBC in a phone call, Professor Eyal Leshem, an infectious disease specialist at Israel's Sheba Medical Center, predicted that in the long run, a two or three-dose vaccination course would probably provide good protection against severe disease for the majority of people.
"We may need to update those boosters every several years, possibly every year, to adjust them to the prevalent variant, but we may well not need any boosters if future variants prove to be less virulent as we see with omicron," he said. "So it is possible that people who have had two or three doses of the current vaccines, and then been exposed during this wave to omicron or are exposed during future waves to other less virulent variants, will not need another booster at all."
Israel began to roll out fourth vaccine doses at the end of last year for older adults, some healthcare workers and people with weakened immune systems.
Leshem conceded that the scientific basis for Israel's rollout of fourth doses was not as robust as it had been for the approval of booster shots, but he said experts had decided to take the measure in case antibodies from boosters waned over time as they had been seen to do so after the initial two doses.
"We really have very little scientific data to suggest that the fourth dose will add a substantially enhanced protection against severe disease and hospitalization," he told CNBC. "So it was a recommendation based on expert opinion, rather than a recommendation based on robust data as we would ideally like to have in clinical medicine. We use expert opinion when we don't have evidence, and we do that all the time in clinical medicine."
Health officials in other countries are currently divided over whether fourth doses of Covid vaccines will be necessary.
Last week, the U.K.'s vaccination authority said there was "no immediate need" to introduce a second booster, although the issue remained under review. The U.S. Centers for Disease Control and Prevention recommends that people who are severely immunocompromised should be given an additional dose in their primary series of vaccines, as well as a booster shot later on.
In December, the CEO of Pfizer told CNBC that fourth doses may be needed sooner than expected because of the highly transmissible omicron variant.
However, the WHO has warned that rolling out too many booster doses in wealthier nations could actually prolong the pandemic by depriving poorer countries of access to vaccines.
Israel has embarked on an aggressive vaccination program in a bid to tame the pandemic and had one of the fastest vaccine rollouts in the world.
As of Sunday, around 71% of Israel's population had received at least one dose of a Covid vaccine, with 64% having been immunized with two doses. Almost half of the population has been given a booster shot.
People who received their second shot more than six months ago are no longer considered fully vaccinated in Israel, where booster shots have been available to everyone over 12 since the summer.
In Israel, individuals must show their vaccination status — or that they have recently recovered from Covid-19 — in order to enter certain venues, including gyms, restaurants and museums.
The country logged 30,970 new cases of the virus on Sunday — the highest number of positive tests in one day since mass testing began.
In the week ending Jan. 9, 136,569 people in Israel tested positive for Covid-19, marking an increase of 331% from a week earlier.
According to official data, the virus' R number — the rate at which it reproduces — has surpassed two, meaning the average infected person will spread Covid-19 to two other people. Any R number above one means an epidemic is growing exponentially.
Hospitalizations in Israel are also on the rise but are nowhere near their pandemic peak. The seven days to Jan. 8 saw 733 hospital admissions, according to Our World in Data, marking the highest weekly number since the omicron variant emerged. Israel's hospitalization rate peaked in Jan. 2021, when 1,985 people were admitted to hospital in one week.
However, fatalities have remained stagnant through the omicron wave in Israel.
On Sunday, one Covid-19 patient passed away in the country. That individual was vaccinated. On average, two people have died from Covid-19 each day over the past month. In late January last year, Israel recorded a high of more than 60 deaths in one day.
Leshem told CNBC that the rate of severe illness and hospitalizations could still rise, as there was usually a lag between rising cases and their consequences.
"However, we don't think that we will see a sharp increase as we would expect with previous variants," he said. Omicron appears "inherently milder in most people, and this may have to do with viral biology — its affinity to the upper airways as contrary to affinity to the lower airways, which causes pneumonia."
He added that the high uptake of booster shots in Israel, as well as the country's young population, were also likely to suppress any significant rise in severe disease.