Every fall, pharmacies fill with fresh influenza vaccines, tailored for nature’s latest version of that miserable bug after it emerges half a world away. As the COVID-19 vaccines’ protection wanes against newer variants of the coronavirus, like omicron, shouldn’t those shots be reformulated as well?
“It’s time for an updated version,” Dr. Michael Lin, an associate professor of neurobiology and bioengineering at Stanford University, said on Twitter this past week after a fourth dose of Pfizer’s COVID-19 vaccine delivered only partial protection against infection from the virus, according to a study in Israel. “They said it would be easy so just do it already.”
But Lin and other experts also acknowledge tailoring COVID-19 vaccines to new variants and getting them out quickly isn’t simple with the virus mutating unpredictably every few months, sometimes harmlessly and sometimes not.
“With the flu, we can predict what we’ll see in the winter, but with COVID, it’s shape-shifting, you’re playing Whac-A-Mole because who knows what’s coming next,” said Dr. Peter Chin-Hong, a medical professor and infectious disease specialist at UC San Francisco. “That’s why it’s so frustrating.”
In an interview, Lin said the biggest obstacle to updating vaccines isn’t technology but logistics and government leadership. The current formulation is already in the distribution pipeline, and government leaders haven’t urged drugmakers to replace it with a new one.
Just a year ago, the current crop of COVID vaccines seemed nothing short of miraculous. Though new vaccines usually take years to develop and receive federal approval, the first ones to combat the coronavirus were produced within a year. And the new messenger-RNA technology of Pfizer and Moderna’s shots held the promise of quick and easy updates.
Initially, two doses of Pfizer or Moderna were about 95% effective and Johnson & Johnson’s one-shot vaccine was around 72% at preventing COVID-19. Flu vaccines by comparison are typically 40-60% effective at preventing illness.
But hopes the COVID vaccines soon would deliver “herd immunity” and snuff out the pandemic faded last summer as they proved less effective against the voracious and deadly delta variant. By the fall, post-vaccine antibodies that are the body’s first line of defense against infection began to fade, leading health officials to recommend a “booster” shot for Pfizer or Moderna after five months, and for J&J after two months.
So far, the vaccines remain effective at keeping people from being hospitalized or dying from COVID-19 by producing a response from so-called memory cells that kick in to help the body beat back a viral infection.
And reports Friday from the Centers for Disease Control and Prevention backed the notion that vaccines still do a very good job at preventing infection by delta and omicron. The CDC found that cases of delta among the unvaccinated were four times higher than people who were vaccinated, and 14 times higher than those who had received a booster. Cases of omicron among the unvaccinated were likewise nearly three times higher than among the vaccinated and five times more than those who had received a booster shot.
Another CDC report also found that boosters were 94% effective at preventing hospitalizations against delta and 90% against omicron.
That’s prompted debate among health experts about whether they should accept that as good enough and give up on additional boosters that only temporarily elevate protection against infection and disease spread.
“No matter what vaccine you give, antibodies are going to decline in three to six months, so they’re probably never going to prevent infection,” Chin-Hong said. “But with the current vaccines, we’re preventing severe hospitalization and deaths.”
That’s how the vaccine-makers are looking at things for the moment.
When asked about updating its vaccine, Pfizer said in a statement it is evaluating an additional dose of both the current formulation and an omicron-specific formulation of its vaccine, as well as “real-world data” such as that from Israel on use of a fourth dose, “to ensure we stay vigilant in addressing the pandemic.”
Moderna said “given the long-term threat demonstrated by omicron’s immune escape,” the company will continue to develop an omicron-specific variant vaccine that it expects to advance into clinical trials early this year. If effective, that vaccine could help in the company’s efforts to develop a multivalent booster that would work against many variants.
Johnson & Johnson said it “will continue to test the effectiveness of our vaccine against new and emerging variants,” while “assessing the need for an update.”
The recent experience in Israel with a fourth shot has been discouraging about prospects for repeated boosters elevating antibody levels enough to block infection and disease spread. Even after 500,000 people age 60 and older got fourth shots, Israel has seen new cases hit records and hospitalizations rise.
An Israeli hospital reported Monday that staff who had been vaccinated and boosted with Pfizer and given a fourth shot of Pfizer or Moderna last month had increased antibody levels but still got infected at almost the same rate as those who didn’t have the fourth shot.
In another blow against repeated boosters of the original vaccine formula, the European Medicines Agency last week said frequent doses could weaken people’s immune responses and tire them out, and recommended annual shots similar to those for influenza.
With the virus mutating so rapidly, any vaccine aimed at today’s variant is outdated once it’s ready to roll out. But Lin said vaccines against earlier variants still may prove more effective than the current one against new variants and should be made available. Even a multivalent vaccine he said would be based on past variants.
An updated vaccine would have to go through additional regulatory review for effectiveness and safety. And the Food and Drug Administration aims to coordinate when and how to update vaccines internationally, as it does with flu shots, according to health news site Stat, adding a layer of bureaucracy and time to roll it out.
“It’s a tough landscape,” Chin said, “and there’s no right answer.”
Source: www.mercurynews.com