Vaccine manufacturers Pfizer and BioNTech face the threat of a more infectious Delta variant and on Thursday released a statement saying it “may be beneficial” for people to get a third dose of their COVID vaccine within six months to a year. But U.S. health officials and other researchers strongly disagree, saying our current vaccines hold up really well – at least so far.
“Americans who have been fully vaccinated do not need a booster shot at this point,” reads an unusual joint statement from the FDA, and the CDC was released hours after Pfizer̵
It is reasonable to endure a booster, researchers told BuzzFeed News, both because our vaccines still keep infections against current variants and because even in the rare cases when vaccinated people become infected, they are protected from serious illness and death.
“The dam is still holding on, even though there has been some splashing,” said immunologist E. John Wherry, director of the Penn Institute of Immunology.
The strength of the vaccines, combined with the fact that Delta has quickly become the dominant strain of the virus circulating in the United States, only increases the urgency for more people to be fully vaccinated, health officials said. In some parts of the US, more than 80% of the new COVID-19 cases are Delta, and this is linked to increases in the UK and Africa with a wave feared for Europe in August.
“Preliminary data from several states over the past few months suggest that 99.5% of COVID-19 deaths in the United States were in unvaccinated people,” CDC chief Rochelle Walensky said Thursday. “These deaths could be prevented with a simple, safe shot.”
Clinical trials with the mRNA vaccines last year reported an astonishingly good, approx. 95% prevention of infections of the original coronavirus strain. While recent studies on the effectiveness of Pfizer’s two-shot mRNA vaccine against the Delta variant in the UK and Canada have shown a slight decrease in the protection offered by the shots, two doses still reduce the risk of infections by 79% to 88%. The Israeli health authority announced unpublished results in May, suggesting that protection against Delta was lowered to 64%, but even then the shots were 93% effective in preventing serious illness and death.
Even the one-shot Johnson & Johnson vaccine, which is approved in the United States but used less frequently, offers reasonably good protection against Delta, Anthony Fauci, head of the National Institutes of Allergy and Infectious Diseases, said during a briefing Thursday at the White House. . He added that the vaccine still reduces the risk of hospitalization by 93%.
“If you had told any of us that this is the effectiveness we have now with vaccines a year ago, we would have run for that deal,” Wherry said. “We are talking about a very significant efficiency rate that could have a major impact on limiting the pandemic.”
Fauci and other experts stressed the emergence of more contagious variants as just another reason why the 32% of American adults are still not vaccinated to get their shots. “Get vaccinated. It will protect you from the increase in the Delta variant, ”said Fauci.
Variant Time Bomb
Still, as long as the virus replicates in humans, it will mutate and give rise to new strains, said immunologist Andrew Pekosz of the Johns Hopkins Bloomberg School of Public Health.
Some of these strains have mutations that make them more contagious. The Delta strain is, for example, approx. 2.5 times more likely to infect unvaccinated people under 50 years of age. And these mutations can also make the viruses less recognizable to our immune systems, which have been trained by vaccines to target the original coronavirus.
The latest variant of concern is Lambda, which was marked by the World Health Organization as a “variant of interest” in June. While an initial study in Chile suggests that, like some other variants, it lowers the effectiveness of vaccines, but more studies are needed.
“The problem is the variants we do not know and where they would be generated,” said Jerome Kim, director of the International Vaccine Institute, a nonprofit focusing on global vaccine development based in South Korea. “The risk is that if we continue to allow significant parts of the globe to be unvaccinated, then we are putting ourselves and all our investment and time at risk and really undermining a year of really intense scientific effort.”
It presents yet another argument against delivering booster shots to humans as soon as those shots could be used to deliver vaccines to those who are still unvaccinated. Even ignoring humanitarian concerns and getting vaccines out to the rest of the world is the best way to stop the emergence of variants that can threaten everyone.
While mutations can help the virus, there are only so many changes it can make without compromising on what makes coronavirus so effective in the first place: the core proteins it relies on to infect cells. “The amount of evolutionary search space that the virus can explore is limited by the fact that the virus tip actually has many jobs to do,” Wherry said. “You can only change so many parts without actually destroying the virus itself. So we will not see an infinite number of variants. ”
That partly explains why our vaccines still work just as well as they do against current variants: Vaccinated immune systems level defenses that are key to those parts of the spike protein that have not yet been mutated. “One or two days after an infection, the immune system, which is ready, begins to hit the virus hard,” Pekosz said.
The Achilles heel of the virus
The same biological timing may explain why even when vaccinated people receive COVID-19, they are less likely to become seriously ill, be hospitalized, or die.
As viral diseases progress, COVID-19 is “a slow burn,” said Deepta Bhattacharya, an immunologist at the University of Arizona. In the early days, when it is most contagious, people experience cold symptoms or no symptoms at all. In severe cases, people can after approx. a week continue to develop dangerous lung infections, caused by our immune system, which goes into disarray and attacks vital organs.
This two-stage disease that was made containing the disease without vaccines is almost impossible, as the early asymptomatic days allow people to transmit the virus “when they do not even know they are sick,” Bhattacharya said.
“It simply came to our notice then. But from an immunological point of view, now with the vaccines, it’s actually good because it buys the immune system a while to clear out the virus before it starts causing major problems, “Bhattacharya added, calling this two-step attack the coronavirus’ Achilles heel ”. ”
In addition to antibodies, the immune system produces so-called memory cells, which may also explain how well our vaccines offer protection against serious illness, said Brian Lichty, an immunologist at McMasters University, in an email. While even fully vaccinated people may have a reduced ability to block infection from variants, as the antibodies are no longer a perfect match for the virus, their memory immune cells can still blunt the infection while developing new immunity to the variant.
Lichty tested an experimental vaccine that was only intended to produce memory cells targeted at non-spike parts of the original coronavirus, finding that it still helped protect mice from variants. “This is not very surprising,” Lichty said via email. “There is still some replication of SARS-CoV2 in these mice, but it is not blocked but only reduced.”
New studies have shown that memory cells can offer protection for at least eight months, providing even more security as more infectious strains emerge. “Almost no matter what, I do not think you are going to fall back and end up back where you were when you had not been vaccinated at all,” Bhattacharya said.
Shortly after serious illness, vaccination is also likely to moderate the eerie symptoms of an infection that does not qualify as serious but is still not fun.
“There is a big difference between having a headache for a few hours and being knocked flat for two days or losing the sense of smell for life,” Bhattacharya said.
When to Boost
Given the current effectiveness of vaccines against variants, the caution expressed by the CDC and the FDA for a booster right now makes sense, experts told BuzzFeed News. But that still leaves open the question of when a booster might be needed.
First, there is an urgent need for more genome sequencing in Africa, Latin America, South America, and parts of Asia where outbreaks occur, as well as less vaccinated parts of the United States to prevent being surprised by a particularly dangerous new strain.
“How many times do we have to learn the lesson that this is a disease that we can predict?” asked Kim. “Unvaccinated people are at risk. You may not have an outbreak now, but you will have an outbreak, and when it does, you will be taken into consciousness, hospital beds will be filled up, intensive care units will be filled up, and people will die. ”
The ultimate goal is to get enough people vaccinated around the world so that the virus cannot spread easily and have fewer chances of mutating. If COVID-19 can become a non-fatal disease like the common cold, the decision to boost it becomes more a matter of how long the immunity from the vaccines lasts. (Although worth noting, people on chemotherapy or with HIV may have boosters faster to increase their immunity to the virus.)
One of the benefits of the mRNA vaccines approved by the United States is that they can be fine-tuned to a particular variant much faster – on the scale of weeks instead of months, as older vaccines. Influenza vaccines grown in eggs, for example, typically have their design chosen in February against an influenza season that only begins in October, giving the virus time to mutate and avoid the shoots. The flexibility of mRNA vaccines gives us the luxury of reacting quickly with a shot if a really dangerous new coronavirus variant emerges before it has that kind of time to mutate further.
“There is also a difference in when you will have to boost and when you need to boost, ”Bhattacharya said. “It is not very likely that variants completely avoid vaccines in our lifetime, but it can get to the point where they avoid enough of it that it is a nuisance and you want to boost. But again, this is a very different situation than what we are in right now. ”