Covid vaccines remain ‘stunningly effective,’ even as delta concerns

Covid-19 vaccines are still “stunningly effective” despite fears that immunity may dwindle over time, experts say.

There have been some concerns about the efficacy of Covid-19 vaccines after a number of recent studies indicated a growing number of so-called “breakthrough” Covid cases among the fully vaccinated. The studies have, however, shown that the fully vaccinated are still highly protected against severe infection, hospitalization and death caused by the virus.

Preliminary data published by the Israeli government in July showed that the Pfizer vaccine was just 16% effective against symptomatic infection for people who had received two doses in January. For people who had been fully vaccinated by April, the vaccine was 79% effective against symptomatic infection, suggesting that immunity gained through immunization depletes over time.

A piece of research funded by Pfizer, published in July, showed that the efficacy of the Pfizer-BioNTech vaccine was strongest between one week and two months after receiving the second dose, coming in at 96.2%. It then, however, declined by an average of 6% every two months. Four to six months after a second dose, its effectiveness fell to around 84%.

In August, meanwhile, a U.K. study of more than one million fully vaccinated people found that protection from both the Oxford-AstraZeneca and the Pfizer-BioNTech vaccines faded over time. A month after receiving a second dose of the Pfizer vaccine, protection against the virus stood at 88%, the analysis showed. After five to six months, that protection fell to 74%.

Protection stood at 77% a month after being fully vaccinated with the Oxford-AstraZeneca vaccine, and fell to 67% after four to five months.

In late July, Israel began offering everyone over the age of 60 a third vaccine dose. Its booster program has been rapidly expanded and third shots have been available to everyone over the age of 30 in the country since August.

Professor Eyal Leshem, an infectious disease specialist at Sheba Medical Center who has been treating Covid patients in Israel, told CNBC that while cases were rising despite a high vaccination rate, the rate of severe illness in the country remained “substantially lower.”

“We attribute that to the fact that most of our adult population is vaccinated with two doses, and more than one million people have received the third booster dose,” he said on a phone call.

“The severe disease rates in the vaccinated are about one-tenth of those seen in the unvaccinated, which means the vaccine is still over 90% effective in preventing severe disease,” Leshem added. “People who received the booster dose are also at much, much…