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World leaders challenge health experts to mix up COVID-19 vaccines as fears over Delta variant grow

BARCELONA – German Chancellor Angela Merkel has done it. Just like the Prime Minister of Canada Justin Trudeau and the Italian Prime Minister Mario Draghi. They have resisted advice from health agencies and mixed up their COVID-19 vaccines after doubts about the effectiveness of the AstraZeneca version against the Delta variant began to circulate.

In what appears to be a growing trend across Europe, the three leaders were first given a dose of an adenovirus vaccine (AstraZeneca) before switching to an mRNA for the second. Merkel and Trudeau took Moderna’s COVID hit for their second, while Draghi opted for Pfizer, neglecting advice from agencies like the Centers for Disease Control and Prevention, which warn against treating them as interchangeable.

Mixing and combining different types of vaccines – an “off-label” practice currently not approved by the World Health Organization – is now common practice in Canada and 15 European countries, and has started to gain traction in the United States. , where there is growing concern over whether the Johnson & Johnson vaccine provides robust enough protection for the Delta variant.

However, questions abound about the safety and effectiveness of this approach.

“We are in a dark and hazy fog of evidence. It’s like a fog of war, ”Dr. Eric Feigl-Ding, senior researcher at the Federation of American Scientists, told Yahoo News.

World leaders challenge health experts to mix up COVID-19 vaccines as fears over Delta variant grow

Canadian Prime Minister Justin Trudeau received a dose of the AstraZeneca vaccine in Ottawa in April. (Adrian Wyld / CP / Bloomberg via Getty Images)

Former WHO director of crisis management Daniel López-Acuna, based in Spain, a country where mixing of vaccine doses has spread, agreed that there is too little evidence to show if the practice makes sense.

“We have to accept that we are in a gray area in terms of the evidence needed to make a good decision,” López-Acuna told Yahoo News.

The controversial practice on Thursday received a proverbial blow in the arm when the European Center for Disease Prevention and Control (ECDC) released a report that found the mix of doses could generate a ‘robust response’ against COVID-19 .

“Data from heterologous (‘mix and match’) vaccination studies suggest that the combination of [AstraZeneca] and mRNA vaccines induce a strong [antibody] against SARS-CoV-2 and elicit a higher T cell response than homologous combinations, ”the report states.

“There is a good immune response to such combinations”, Karam Adel Ali, a politician communicable disease expert at ECDC, told Yahoo News, adding that although the combination may produce more side effects, “mixed programs appear to be generally well tolerated.”

According to the report, other recent studies and the German government, the combo may even be better at boosting immunity than two doses of the same drug, especially AstraZeneca, which preliminary research suggests is less effective than vaccines. to mRNA to fight Delta and Beta Variants.

World leaders challenge health experts to mix up COVID-19 vaccines as fears over Delta variant grow

Vials of Oxford / AstraZeneca COVID-19 vaccine are kept in a refrigerator at a vaccination center in London. (Dinendra Haria / SOPA Images / LightRocket via Getty Images)

“It’s a bit of a dangerous trend here where people find themselves in an area with no data and no evidence when it comes to mix-and-match,” noted Dr Soumya Swaminathan, WHO chief scientist, at an online press conference. week, before specifying via tweet a few hours later that it was referring to individuals, and not to health agencies.

WHO does not broadly support the mixing of different vaccines, except when supplies of the first vaccine are not available.

“For better protection, WHO recommends that two doses of a two-dose schedule be given, at the recommended intervals,” Dr Siddhartha Datta, program manager for immunization and preventable diseases, told Yahoo News. vaccination at WHO Europe, adding that “WHO recommends that the same product be used for both doses”.

Even Pfizer is wary of the blended approach, as noted in its media office’s written response to Yahoo News. “Interchangeability is not part of the current regulatory authorizations for the [Pfizer-BioNTech] vaccine. As a biopharmaceutical company operating in a highly regulated industry, our position is supported by the label and indication agreed with the regulators and informed by data from our Phase 3 study, ”the company said in a statement sent by email. “Therefore, we are currently unable to support mixed schedules. “

But countries that initially relied heavily on AstraZeneca’s adenovirus vaccine (such as Canada, where a quarter of vaccinated citizens received different types of vaccines) report several recent studies, one in Spain and another in the Kingdom. United, which have shown beneficial results.

World leaders challenge health experts to mix up COVID-19 vaccines as fears over Delta variant grow

A nurse prepares a dose of the Pfizer-BioNTech vaccine in Quito, Ecuador. (Rodrigo Buendia / AFP via Getty Images)

For López-Acuna, all vaccines tend to be less effective against the newer variants, especially single-shot vaccines. A recent study published in the New England Journal of Medicine showed that an injection of AstraZeneca or Pfizer was only 30% effective in protecting against the highly contagious Delta variant. (With two doses, the Pfizer vaccine showed 88% effectiveness against Delta, while AstraZeneca showed 67%.)

“We must continue to vaccinate and supplement the schedule of those who have only one vaccine,” he said, adding that countries like Spain, where Delta is exploding, must maintain distancing restrictions social and measures like closing nightclubs in place.

Feigl-Ding, however, is open to at least considering the viability of the vaccine mix. “The WHO chief scientist doesn’t really like [mixing vaccines] because it’s like we’re in a world without evidence. But in some ways, a lot is in a world without evidence. You know, we don’t have a randomized trial for parachute wearing and death prevention. It makes sense for parachutes to slow you down and prevent it.

Richard Carpiano, professor of public policy and sociology at the University of California at Riverside, told Yahoo News he understands how uncertainty can be mistaken for instability.

“We are waiting for definitive answers from scientists and clinicians. But that’s not how most normal science works. Due to an ever-changing situation for a coronavirus that was little known to us just over a year ago, the scientific community is moving fast to understand it and the guidelines are frequently updated. It’s actually the science that works as it should, ”he said. “However, for much of the general public, this continuing update risks being seen as science and public health officials not knowing what they are doing.”

World leaders challenge health experts to mix up COVID-19 vaccines as fears over Delta variant grow

Woman receives Pfizer COVID-19 vaccine at mobile clinic in East Los Angeles, Calif. (Frederic J. Brown / AFP via Getty Images)

It is also unclear how effective mixing with the J&J vaccine is, said Feigl-Ding, who, according to unpaired results, is also significantly less effective than mRNA injections against COVID variants. -19.

For Dr Peter Hotez, vaccine scientist at Baylor College of Medicine, the biggest problem is getting everyone vaccinated, including people in the poorest parts of the world like Africa, where less than 1% of the population received a COVID vaccine.

“No vaccine is perfect,” he told Yahoo News. “But I think we can get vaccinated to get out of this. I think we’ll probably need a third vaccination to do that, at some point, but I think if we can get enough people vaccinated, I think we can vaccinate to get out of this epidemic. “


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