Are Covid vaccines becoming less effective?

Covid-19 vaccines are still “incredibly effective” despite fears that immunity may decline over time, experts said.

There have been some concerns about the effectiveness of Covid-19 vaccines after several recent studies indicated an increasing number of so-called “advanced” cases of Covid among fully vaccinated people. However, studies have shown that fully vaccinated people are still highly protected against serious infections, hospitalization and death caused by the virus.

Preliminary data released by the Israeli government in July, the Pfizer vaccine was shown to be only 16% effective against symptomatic infection in people who had received two doses in January. For people who had been fully vaccinated in April, the vaccine was 79% effective against symptomatic infection, suggesting that the immunity gained through immunization wears off over time.

A Pfizer-funded study, published in July, showed that the effectiveness of the Pfizer-BioNTech vaccine was stronger between one week and two months after receiving the second dose, at 96.2%. However, it decreased by an average of 6% every two months. Four to six months after a second dose, its effectiveness dropped by about 84%.

Meanwhile, in August, a study in the UK with more than a million people fully vaccinated found that protection against Oxford-AstraZeneca and Pfizer-BioNTech vaccines faded over time. One month after receiving a second dose of the Pfizer vaccine, protection against the virus stood at 88%, according to the analysis. After five to six months, this protection fell to 74%.

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

In late July, Israel began offering a third dose of vaccine to all over-60s. Its reinforcement program has expanded rapidly and since August there have been third shots available for all over 30s in the country.

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

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

“Serious disease rates in vaccinated people are about one-tenth of those observed in unvaccinated people, which means the vaccine is still more than 90% effective in preventing serious diseases,” Leshem added. “People who received the booster dose also have a much lower risk of becoming infected, as our short-term data show.”

Richard Reithinger, an infectious disease expert and vice president of global health at U.S.-based RTI International, told CNBC by email that most vaccines developed against Covid-19 were “nothing short of surprisingly effective, until and all with the new emerging variants “.

“Irrefutable proof of this is how cases, serious illnesses requiring hospitalization and deaths fell dramatically in countries that rapidly increased vaccination coverage,” he said.

“In countries with very high vaccine coverage, such as Iceland with more than 90%, almost no serious cases are reported and deaths occur. Similarly, in countries with moderate to high vaccine coverage, such as the US and Canada. , serious cases and deaths occur almost exclusively in unvaccinated people “.

An earlier English study, published in May, found that the Pfizer-BioNTech vaccine was 88% effective in preventing symptomatic delta variant diseases. Against the alpha variant, once the dominant strain in the UK, the vaccine was 93% effective in preventing symptomatic disease.

Meanwhile, research found that two doses of the Oxford-AstraZeneca vaccine were 60% effective in preventing symptomatic delta variant disease, compared with a 66% efficacy rate against the alpha variant.

The data showed the importance of having two doses of these vaccines, as the efficacy of both shots against symptomatic infection of the delta variant stood at only 33% three weeks after the first dose, according to the ‘study.

Reithinger told CNBC that if the virus continued to mutate, it did not mean it was more resistant to existing vaccines.

“The delta variant has been shown to be more transmissible than other variants and the efficacy of the vaccine is slightly lower than that of the alpha and beta variants. The kappa variant, which emerged in India at the same time, does not it is so transmissible “. he stressed.

Several other countries, including the United States and the United Kingdom, are now offering – or planning to offer – third doses of Covid-19 vaccines to help boost immunity to the virus that may have been depleted.

According to Gideon Schreiber, a professor at Israel’s Weizmann Institute of Science, reinforcing traits may become a necessity.

“Unfortunately, it is not even [going to be] “The virus has enormous potential for new variants, many of which will work to silence immunity, so there is a possibility that we need more boosters in the future,” he predicted.

Schreiber added that the Israeli reinforcement program seemed, so far, a great success. After a second dose, he told CNBC, people were four to five times less likely to get serious illnesses with Covid. But after a third dose, they were more than ten times less likely to suffer from serious virus diseases.

However, Reithinger argued that booster shots were not necessarily a logical step at this time.

“There is only limited data available that an immune response that was prepared for available vaccines decreases after six to eight months,” he told CNBC by email. “Most of the data refer to infection, rather than hospitalization or death. The data also do not explain the use of non-pharmaceutical interventions, such as masking and social distancing, which in many contexts would have been to continue using and respecting The only population groups for which reinforcement shots can be made are the immunocompromised. “

However, he said booster shots could be needed if the data show the effectiveness of vaccines against serious diseases and death decreases over time.

Schreiber is currently overseeing research into a therapeutic drug that would act as a “super-cork,” physically trapping itself in cellular receptors to which the virus adheres. By working to block the “entry ports” of cells instead of attacking the virus itself, scientists hope to keep abreast of any future mutations.

“It should work against future variants, because it doesn’t really go after the virus; the virus can change, but as long as the virus binds to it, it will block it,” he told CNBC.

However, Schreiber said the drug would not be something that could be used on a large scale.

“It’s too expensive and not necessary,” he said. “My view is that it would be given to people who had Covid and were part of a high-risk group. It also doesn’t have a long-term effect like a vaccine.”

Leshem of Sheba Medical Center argued that vaccinations were currently the best hope society had for finding a state of “equilibrium” with the virus, where the virus could circulate without serious repercussions.

“The best hope for people at risk is vaccination, an effective vaccine, that we currently have, and that can be improved through boosters, mixing, or through other methods,” he said.

“Still a lot [intense] research, it is very difficult to find effective treatments: viruses are not bacteria. So while we’ve developed good antibiotics that have drastically changed the course of bacterial infection, we don’t have such good antivirals for many of the viruses that infect humans. “

Pharmaceutical companies are also studying new treatments to prevent Covid apart from vaccines. In mid-August, AstraZeneca published the results of a phase three trial of an antibody therapy that was found to reduce the risk of developing symptomatic Covid-19 by 77%. There were no deaths or cases of serious illness among the 25 participants who contracted symptomatic Covid during the trial. A total of 5,172 people participated in the trial, 75% of whom had comorbidities.

Reuters reported that AstraZeneca was seeking conditional approval for the therapy in major markets this year. The pharmaceutical giant would produce between 1 and 2 million doses by the end of this year, the news agency said.

“What I really think is that we really need a drug,” Schreiber told CNBC. “There are a lot of efforts in drug development. There’s no reason not to believe it won’t come in the near future. It will come and that, I think, basically, will end the story.”

He added: “The virus continues to mutate: new variants will come, but the speed of technological advances is really amazing. So I say there is no reason to despair.”