Israelis at the beach in Tel Aviv as Israel exits its third COVID-19 lockdown, Feb. 7. 2021. Photo: Miriam Alster/Flash90.

JNS.org – Israel may be unable to achieve herd immunity against COVID-19 even if 100 percent of those eligible to be vaccinated against the disease are inoculated, a Health Ministry expert told the Knesset on Sunday, as the country began lifting its third national lockdown.

Speaking to the Knesset Constitution, Law, and Justice Committee, which had convened to discuss COVID-19 regulations, Dr. Alroy-Preis, head of public-health services at the ministry, said that while Pfizer’s BioNTech COVID-19 vaccine is effective, it may not be effective enough. Compounding the issue, she said, is that none of the currently available vaccines may be administered to children.

“At the moment we have 2.5 million children who can’t be vaccinated… [and] the Pfizer vaccine is 95 percent effective, which means that 5 percent won’t have full protection,” she said, noting that for the older cohort the vaccine’s tested efficacy was even lower, approximately 90 percent.

Herd immunity occurs when a large enough segment of a population community becomes immune to a disease, rendering its further spread unlikely. Once herd immunity is achieved, even those members of the population that are not immune are protected.

The exact percentage of the population that must be immune in order for herd immunity to be achieved varies depending on the disease. As a general rule, the more contagious the disease, the higher the percentage needed.

According to the World Health Organization, herd immunity against measles requires about 95 percent of a population to be vaccinated, while for polio the threshold is about 80 percent. The figure for COVID-19 is not known, according to the WHO, and “will likely vary according to the community, the vaccine, the populations prioritized for vaccination, and other factors.”

The highly contagious UK variant of the COVID-19 virus has “changed the game” in Israel, warned Alroy-Preis.

“We’re in a situation in which the [virus’s reproduction number is one], and we’re relaxing restrictions,” she warned.

While the country has mounted a massive and effective vaccination campaign during the lockdown, she said it might not be sufficient.

“If we thought that after the first round of vaccine shots, everything would be different, that’s not the case. We are seeing mutations [of the COVID-19 virus] around the world that are reinfecting people,” she said.

While more than one-third of the population has received the first dose of the vaccine and nearly a quarter have received the second dose, and despite weeks of lockdown, morbidity remains high, standing at 8.8 percent on Sunday.

The Military Intelligence COVID-19 task force has found that despite a decrease in the number of seriously ill patients, the number of daily new cases remains high and hospitals continue to be overwhelmed. During the lockdown the virus’s reproduction number surpassed one; it now stands at a high 0.99.

According to the task force, this statistic, along with the easing of some lockdown restrictions on Sunday and the prevalence of the UK variant of the virus (Israeli Prime Minister Benjamin Netanyahu said during the Cabinet meeting on Thursday that the variant accounts for some 80 percent of all new cases) is expected to lead to a sharp increase in morbidity in the coming weeks.

Israel already leads Western countries like the United States, United Kingdom, France and Austria in the number of new infections per 1 million people, according to the report.

There has, however, been a decrease in verified cases as well as in severe cases of the disease among patients aged 60 and over, likely due to the influence of the vaccination campaign. More than 15 percent of that age group, however, has neither received the first dose of the vaccine nor recovered from the virus.

Jerusalem’s Herzog Medical Center, which specializes in medical care for the elderly, is currently treating 100 coronavirus patients, 42 of which are in serious condition.

“We have a critical week ahead of us,” said the center’s director, Dr. Jacob Haviv. “The wards are still full with seriously ill patients, and on the other hand, lockdown restrictions have been eased. I call on everyone to go and get vaccinated. The vaccine has proven itself. There are almost no outbreaks in nursing homes. This is a significant success for the vaccine.”

This article first appeared in Israel Hayom.