'Dangerous trend': WHO warns against 'mixing and matching' COVID-19 vaccines

The World Health Organization's chief scientist on Monday called the mixing of the doses of the COVID-19 vaccine as a "dangerous trend,” as she reminded that there was limited data available about the implications of administering two different shots of the vaccine for instance the increasing trend of inoculation with AstraZeneca followed by a second dose of the Pfizer.  "It will be a chaotic situation in countries if citizens start deciding when and who will be taking a second, a third, and a fourth dose,” WHO’s Soumya Swaminathan cautioned at a live-streamed conference on July 12.

"It's a little bit of a dangerous trend here. We are in a data-free, evidence-free zone as far as to mix and match,” WHO's chief scientist said. 

As the more contagious and dangerous delta variant was on the way to becoming the dominant strain worldwide, the WHO last month advised the world’s population to administer whatever vaccine was made available first, even if the said individual had recovered the COVID-19 infection. “It is important to be vaccinated as soon as possible once it’s your turn and not wait,” the global health agency said. “Approved COVID-19 vaccines provide a high degree of protection against getting seriously ill and dying from the disease, although no vaccine is 100 percent protective,” it continued in a statement that prompted many in the countries witnessing the rising trajectory to jab with the available COVID-19 vaccine. Many, however, decided later to switch to mRNA vaccines for the second dose, while the researchers are still gathering data. 

Dr. Kate O’Brien, director of the World Health Organization’s vaccine unit, meanwhile stated, “The authorized COVID-19 shots around the world are all designed to stimulate your immune system to produce virus-fighting antibodies, though the way they do so varies.” He added, “Based on the basic principles of how vaccines work, we do think that the mix-and-match regimens are going to work.” He further continued, “We really just need to get the evidence in each of these (vaccine) combinations.” 

UK researchers testing mixing of vaccines

Researchers at UK’s Oxford University have been testing combinations of the two-dose COVID-19 vaccines made by AstraZeneca, Moderna, Novavax, and Pfizer-BioNTech. Smaller trials are also ongoing in Spain and Germany, The Associated Press learned from sources. Thus far, it reports, that there has been only little data with regard to suggesting that an AstraZeneca shot followed by the Pfizer shot was safe and effective. Although, such nature of vaccine mixing did result in temporary side effects such as fatigue, aches, and chills.

A virologist at the University of Warwick in the United Kingdom argued that the mixing and matching of the COVID-19 vaccines can often produce a stronger immune response, and therefore while no proof exists of it being detrimental, health officials in many countries allowed mixing in select circumstances. Especially after the AstraZeneca shot was linked with the extremely rare blood clots, EU nations rolled out an advisory asking the younger individuals who got it as a first dose to now get a Pfizer or Moderna as the second shot instead.