Juan Rodriguez (L) reacts as he receives the Janssen Covid-19 vaccine from Johnson & Johnson administered by professional nurse Christina Garibay at a Skid Row community event held on August 22, 2021 in Los Angeles, California, Covid-19 vaccines and tests were offered.
Frederic J. Brown | AFP | Getty Images
Covid-19 vaccines are still “amazingly effective,” experts said, despite fears that immunity could wane over time.
There have been some concerns about the effectiveness of Covid-19 vaccines after a number of new studies suggested a growing number of so-called “breakthrough” covid cases among those fully vaccinated. However, the studies have shown that those who are fully vaccinated are still very well protected from serious infections, hospitalizations, and deaths from the virus.
Preliminary data released by the Israeli government in July showed that the Pfizer vaccine was only 16% effective against symptomatic infections in people who received two doses in January. In those who were fully vaccinated by April, the vaccine was 79% effective against symptomatic infections, suggesting that the immunity gained from immunization decreases over time.
A Pfizer-funded study published in July showed that the Pfizer BioNTech vaccine was most effective between one week and two months after receiving the second dose, at 96.2%. After that, however, it decreased by an average of 6% every two months. Four to six months after a second dose, the effectiveness dropped to about 84%.
In August, a UK study of more than a million fully vaccinated people found that protection from both the Oxford-AstraZeneca and Pfizer BioNTech vaccines deteriorated over time. One month after receiving a second dose of the Pfizer vaccine, the protection against the virus was 88%, the analysis showed. After five to six months, this protection dropped to 74%.
Protection was 77% monthly after full vaccination with the Oxford AstraZeneca vaccine and decreased to 67% after four to five months.
Lessons from Israel
In late July, Israel began offering a third dose of vaccine to anyone over 60 years of age. The booster program was quickly expanded, and third syringes have been available to everyone over 30 in the country since August.
Professor Eyal Leshem, an infectious disease specialist at Sheba Medical Center who treats Covid patients in Israel, told CNBC that while the number of cases has increased despite a high vaccination rate, the rate of serious illnesses in the country has remained “much lower” may be.
“We attribute this to the fact that most of our adult population have been vaccinated with two doses and more than a million people have received the third booster dose,” he said on a phone call.
“Serious disease rates among the vaccinated are about a tenth of those among the unvaccinated, which means the vaccine is still over 90% effective in preventing serious illness,” added Leshem. “People who received the booster dose also have a much, much lower risk of getting infected, as our short-term data shows.”
Richard Reithinger, infectious disease expert and vice president of global health at RTI International, based in the US, told CNBC in an email that most of the vaccines developed against Covid-19 “were amazingly effective even with the emerging variants” .
“Undeniable evidence of this is that cases, serious illnesses that required hospitalization, and deaths in countries that have rapidly increased vaccination rates have dramatically decreased,” he said.
“In countries with very high vaccination coverage, like Iceland with more than 90%, hardly any serious cases and deaths are reported. Similarly, in countries with medium to high immunization coverage, such as the United States and Canada, severe cases and deaths are seen almost exclusively in the unvaccinated. “
An earlier UK study published in May found the Pfizer BioNTech vaccine was 88% effective in preventing symptomatic disease caused by the Delta variant. 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 disease from the Delta variant, compared to a 66% effectiveness rate versus the Alpha variant.
The data showed the importance of two doses of these vaccines, as the effectiveness of both vaccinations against symptomatic infections from the Delta variant was only 33% three weeks after the first dose.
Reithinger told CNBC that another mutation in the virus doesn’t necessarily mean it becomes more resistant to existing vaccines.
“The delta variant has been shown to be more transmissible than other variants, and the vaccine effectiveness is slightly less than the alpha and beta variants. The kappa variant that was created around the same time in India is not so transferrable, ”he emphasized.
Are booster shots the solution?
Several more countries, including the US and UK, are now offering or planning to offer third doses of Covid-19 vaccines to help boost immunity to the potentially depleted virus.
According to Gideon Schreiber, a professor at Israel’s Weizmann Institute of Science, booster injections could become a necessity.
“Unfortunately it isn’t even [going to be] “The virus has tremendous potential for new varieties, many of which will help silence immunity – so there is a chance we may need more boosters in the future.”
Schreiber added that Israel’s booster program appears to have been a huge success so far. After a second dose, he told CNBC, the chances of developing Covid were four or five times less likely. But after a third dose, the chances of getting seriously ill with the virus were more than ten times less.
However, Reithinger argued that booster shots weren’t necessarily a logical move at this point.
“There is limited data that an immune response triggered by available vaccines wears off after six to eight months,” he told CNBC via email. “Most of the data relate to infections, not hospitalizations or deaths. The data also does not take into account the use of non-pharmaceutical measures such as masking and social distancing, which should continue to be used and followed in many contexts. The only populations for whom a booster can be given are the immunocompromised. “
However, he said a booster dose may eventually become necessary when data shows the vaccines’ effectiveness against serious illness and death over time.
Hope for treatment?
Schreiber is currently overseeing research into a therapeutic drug that is said to act as a “super cork” and physically wedges itself in cell receptors to which the virus attaches. By working to block the cells’ “entry ports” rather than attacking the virus itself, the scientists hope to keep an eye on future mutations.
“It should work against future variants because it doesn’t really track the virus – the virus can change, but as long as the virus attaches to it, it will block it,” he told CNBC.
However, Schreiber said the drug could not be used on a large scale.
“It’s too expensive and there is no need,” he said. “I see it as being given to people who have Covid and who belong to a high-risk group. It also has no long-term effects like a vaccine.”
The Sheba Medical Center’s Leshem argued that vaccinations are currently society’s best hope of finding a state of “equilibrium” with the virus in which the virus can circulate without serious effects.
“The best hope for people at risk is immunization, an effective vaccine we have right now that can be improved by boosting, mixing, or other methods,” he said.
“Despite very [intense] Research makes it very difficult to find effective treatments – viruses are not bacteria. So while we have developed good antibiotics that have dramatically changed the course of bacterial infections, we don’t have such good antivirals for many of the viruses that infect humans. “
In addition to vaccines, pharmaceutical companies are also looking for new treatment methods to prevent Covid. In mid-August, AstraZeneca published results of a phase 3 study of an antibody therapy that reduced the risk of symptomatic Covid-19 disease by 77%. There were no deaths or cases of serious illness among the 25 participants who became infected with symptomatic Covid during the study. A total of 5,172 people took part in the study, 75% of whom suffered from comorbidities.
Reuters reported that AstraZeneca is seeking conditional approval for the therapy in key markets this year. The pharmaceutical giant will produce 1 to 2 million doses by the end of this year, the news agency said.
“I really think we really need a drug,” Schreiber told CNBC. “There is a lot of drug development effort going on, there is no reason not to believe it won’t come in the near future. It will come and this will basically end history.”
He added, “The virus continues to mutate – new varieties will come, but the rate of technological advances is truly amazing. So I say there is no need to despair. “