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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 first received a dose of an adenovirus vaccine (AstraZeneca) before switching to an mRNA vaccine for the second. Merkel and Trudeau took Moderna’s COVID shot for their follow-up shot, while Draghi opted for Pfizer, neglecting advice from agencies like the Centers for Disease Control and Prevention, which warn against treating vaccines as interchangeable .
Mixing and pairing 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 whether the Johnson & Johnson vaccine provides sufficiently robust protection for the Delta variant.
However, questions abound about the safety and effectiveness of this approach.
“We are in a cloudy, hazy haze of evidence. It’s like a fog of war, ”Dr. Eric Feigl-Ding, senior researcher at the Federation of American Scientists, told Yahoo News.
Former WHO crisis management director Daniel López-Acuña, based in Spain, a country that has led the practice of vaccine mixing, agreed that there was too little evidence to show whether the practice made sense.
“We have to accept that we are in a gray area in terms of the evidence needed to make a good decision,” López-Acuña 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 combat Delta and Beta Variants.
The growing popularity of combination vaccines worries some public health officials. “It’s a bit of a dangerous trend here where people are in an area with no data or evidence when it comes to mix-and-match,” WHO Chief Scientist Dr Soumya Swaminathan noted during from an online press conference last 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 two different types of vaccines) report several recent studies, one in Spain and another in the United States. UK, which have shown beneficial results.
For López-Acuña, all vaccines tend to be less effective against the newer variants, especially when a person has only received the first injection of a two-shot vaccine. A recent study published in the New England Journal of Medicine showed that one dose of AstraZeneca was only 30 percent effective in protecting against the highly contagious Delta variant, while Pfizer was at 36 percent. (With two doses, the Pfizer vaccine showed 88% effectiveness against Delta, while AstraZeneca showed 67%.)
“We must continue to vaccinate and complete the schedule of those who have only one vaccine,” he said, adding that countries like Spain, where Delta is exploding, must maintain curfews and measures such as closing nightclubs.
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 at the University of California at Riverside, told Yahoo News he understands how uncertainty can be mistaken for fragility.
“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 we knew little about just 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.”
It’s 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 specialist at Baylor College of Medicine, the biggest problem is getting everyone vaccinated, including people in the poorest parts of the world like Africa, where only about 1% of the population has been fully vaccinated against COVID.
“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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