A small Israeli study indicates that some of the new coronavirus variants may put people vaccinated at higher risk for breakthrough infections, although US health officials have questioned some of the wording used in the preliminary study.
Cases like this are called “breakthrough infections,” which occur when someone who has completed their COVID-19 vaccination later becomes ill with the virus.
The preprint, published Friday and not peer-reviewed, received attention over the weekend after it was said that the B.1.351 variant was more likely to infect people in Israel who had been vaccinated with Pfizer Inc.’s PFE.
COVID-19 vaccine, compared to other strains of the virus.
There are several documented variants of concern, including the B.1.351, which was first identified in South Africa; the B.1.1.7, first discovered in the UK; and the P.1 from Brazil, which are believed to be easily transferable.
The researchers identified eight cases of breakthrough infections caused by the B.1.351 variant and 134 cases of the B.1.1.7 variant of the approximately 400 people enrolled in the study who tested positive for the vaccine during or after the vaccination period. virus. Oddly enough, the control group of unvaccinated people had only one case caused by B.1.351.
“Our results show a reduced effectiveness against the [South African] variant only in a short time frame (7-13 days after the second dose) as all the breakthrough cases we saw were in this time frame, ”said Adi Stern, a professor at Tel Aviv University and one of the co-authors. in an email. “But again, the caveat is that our sample size is small and this requires further research.”
When asked about the study, federal health officials on Monday downplayed the accuracy of the findings.
“That preprint was as confusing as you could be, as it were,” Dr. Anthony Fauci, President Joe Biden’s chief medical adviser, told reporters at a White House briefing. It seemed that you were more likely to have the [B.1.]351 if you have in fact been vaccinated against the mRNA. That was not the case. If you were to get infected with something, you would get infected with the more difficult variant, namely 351. That does not mean that you have a greater chance of getting it. “
Pfizer addressed questions about the study to the authors.
What we know so far about vaccines and variants
Fauci said clinical data to date points to the mRNA vaccines developed by Pfizer and BioNTech SE BNTX,
as well as Moderna Inc. MRNA,
still provide protection against B.1.1.7, but the vaccine’s efficacy is thought to be declining against the B.1.351 variant, which is a less common strain of the virus at this time, at least in the US.
Both mRNA vaccines had very high efficacy rates in Phase 3 clinical studies, with each reporting about 95%, although the studies were conducted last fall, before two of these new variants were detected. According to at least one prepress study published by the Mayo Clinic in February, the actual effectiveness of both vaccines is believed to be closer to 89%, but that’s still considered a very strong level of protection against the virus.
Here’s what we know – and don’t know – about ‘breakthrough infections’
While getting COVID-19 shots can drastically reduce the chances of someone becoming infected with the virus, breakthrough infections for vaccinees are still possible, especially with these new, more contagious variants of the coronavirus circulating around the world.
Moderna said last month it will initiate clinical trials, in partnership with the National Institutes of Health, on a vaccine specifically designed to provide protection against the B.1.351 variant. Pfizer is also testing a booster shot and a new vaccine specifically targeting the South African variety.
“What we do know when these breakthrough infections occur is that they usually occur with fewer symptoms, fewer viruses, [and] less transmissible virus, ”said Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, at the same briefing on Monday. “We are still learning about the transmissibility of this virus in the context of these breakthrough infections.”
Breakthrough infections can also occur if immunity wanes, the shot is damaged by a storage problem, for example, or if a person’s age or medications limit their immune response, Fauci added.
This is why Americans are paying close attention to Israel’s vaccination campaign
Of all the countries in the world with vaccination campaigns, Israel has vaccinated the largest percentage of its inhabitants. According to a government dashboard, about 53% of people in Israel have been fully vaccinated since Sunday. In comparison, the US has vaccinated about 22% of its, albeit much larger, population since Monday, according to the CDC.
Pfizer’s vaccine is the predominant shot used in the Israeli campaign, and so countries that also rely on that drug manufacturer’s vaccine are curious to see what real-world data is coming out of Israel right now, even though there are significant differences between immunization protocols between countries.
The Israeli study also found that the B.1.1.7 variant (UK) is the most dominant form of the virus in Israel (as in the US), although the strain B.1.351 (South Africa) has less than 1 %. of the cases included in the study.
“There may be higher breakthrough rates with B.1.351, but it is possible that (a) the effectiveness of the vaccine in combination with performed non-pharmaceutical interventions remains sufficient to prevent its spread, and / or (b) B.1.1 .7
outperforms B.1.351, possibly due to the high transmission speed, ”concluded the researchers.