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As the highly transmissible Delta variant of the coronavirus spreads to dozens of countries around the world, several governments are mixing vaccines in an attempt to boost their vaccination campaigns.
Mixing vaccines means administering a brand of vaccine for a patient’s first injection, followed by a vaccine made by a different manufacturer for the second dose. Proponents of the policy believe it can increase the speed and effectiveness of vaccination campaigns.
Several ongoing studies are investigating the effects of mixing coronavirus injections. Data has been published from mixed trials in Spain and the UK, which suggests that the vaccine mixture causes a strong immune response and sometimes surpasses two doses of the same vaccine.
In Germany, a third study also found that the immune response of mixing doses of the coronavirus was better than two injections of AstraZeneca and as good or better than receiving two doses of the Pfizer vaccine.
Which countries are mixing vaccines?
Several countries, including Bahrain, Bhutan, Canada, Italy, South Korea, Thailand and the United Arab Emirates, have started mixing vaccines as policy.
The practice was quietly cleared in January by England’s Public Health when vaccine supplies were tight.
That same month, US media reported that the Centers for Disease Control and Prevention in the United States relaxed their recommendations allowing mixing “under exceptional circumstances.”
In March, several countries halted their vaccination campaigns over concerns over extremely rare blood clots associated with the Oxford-AstraZeneca vaccine.
In response, in some countries, health workers have been allowed to administer a different vaccine for the second vaccine to some patients who received the AstraZeneca vaccine for their first vaccine.
Dr Gloria Taliani, professor of infectious diseases at Sapienza University in Rome, told Al Jazeera that the mixture was common in the treatment of other diseases in the past.
“We used different vaccines [when we treated] other diseases and we don’t care if the second dose is a different vaccine from the first, or if the booster dose is different.
Dr Taliani noted that there might be questions as this is the first time that mRNA vaccines have been used to protect against infectious diseases, but said there was no biological reason to suggest that the mixing could be dangerous.
“There is no biological reason why vaccines that use a different stimulus for the immune system could be harmful to anyone,” she explained.
Several world leaders have mixed vaccines in recent months. German Chancellor Angela Merkel, 66, received a second dose of Moderna vaccine after receiving a first dose of AstraZeneca.
In Italy, Prime Minister Mario Draghi, 73, switched to Pfizer for his second dose after receiving an injection of AstraZeneca. Canadian Prime Minister Justin Trudeau also changed his vaccine, receiving an injection of Moderna after an injection of AstraZeneca.
Prime Minister of Canada Justin Trudeau receives his second dose of Moderna coronavirus disease (COVID-19) vaccine at a pharmacy in Ottawa [File: Blair Gable/Reuters]Is the COVID vaccine mixture effective?
The University of Oxford’s Com-COV trial, involving more than 800 volunteers, investigated the effectiveness of two doses of AstraZeneca, Pfizer, or one followed by the other.
According to the results, mixed regimens involving the Pfizer vaccine and the AstraZeneca vaccine generated a strong immune response against the virus.
The results of the study suggest that the order of the vaccines made a difference, with AstraZeneca followed by Pfizer “inducing higher antibodies and T cell responses than Pfizer followed by AstraZeneca”.
T cells stimulate the production of antibodies and help fight cells infected with the virus. Research has also shown that two doses of Pfizer produced the highest level of antibodies.
The two mixtures produced better results than the still very effective AstraZeneca two-dose vaccines.
Separately, in May, a Spanish study involving more than 600 volunteers found that one AstraZeneca followed by Pfizer was more effective than two doses of AstraZeneca.
However, experts say there is a lack of sufficient clinical data to fully determine whether the mixture is effective.
Dr. Anna Blakney, Assistant Professor at the Michael Smith Laboratories and the School of Biomedical Engineering at the University of British Columbia, was part of a team that conducted a trial to mix an mRNA vaccine and the vaccine. AstraZeneca viral vector.
“What we saw in mice was that the combination of these two was more effective than either alone,” she said.
“So I think it can work, but we don’t have the data yet to say if it’s a really effective diet.”
Is it Safe to Mix COVID Vaccines?
No results from the studies have suggested that the mixture causes serious side effects, but the results of the UK study suggest that the mixture of vaccines may lead to an increase in mild or moderate side effects.
Data from the Com-COV study showed that 30 to 40 percent of those who received mixed doses reported fevers after a second dose, compared with 10 to 20 percent of those who did not mix the vaccines. .
“The results of this study suggest that mixed dose schedules could lead to an increase in absences from work the day after vaccination, and it is important to take this into account when planning the vaccination of healthcare workers,” Dr Matthew Snape, associate professor of pediatrics and vaccinology at the University of Oxford and the trial’s chief investigator said at the time.
The ongoing Com-COV trial expanded to include Moderna and Novavax vaccines in April.
Results from the Spanish study revealed that mild side effects were common and similar to those reported with two doses of the same vaccine.
Meanwhile, World Health Organization chief scientist Soumya Swaminathan has warned individuals against the option of mixing vaccines and said decisions should be left to health agencies.
“Individuals shouldn’t decide for themselves, public health agencies can, based on the data available,” Swaminathan said in a tweet. “Data from mix and match studies of different vaccines are awaited – both immunogenicity and safety need to be evaluated.”
Trial results suggest that the mixed schedules involving the Pfizer and Oxford vaccine generated a strong immune response against the virus [File: AFP]
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