According to a study, mixing Covid shots produces a positive immunological response.
According to a UK study, a mix-and-match approach to Covid vaccinations (using different brands for the first and second doses) appears to provide good protection against the pandemic virus.
The Com-Cov experiment compared the efficacy of two Pfizer doses, two AstraZeneca doses, or one of each followed by the other.
The immune system was primed by all of the combinations.
Experts believe that this knowledge could help with vaccination deployment flexibility.
The findings also suggest that those who have already gotten two doses of the AstraZeneca vaccine may have a higher immune response if a different vaccine is given as a booster in the autumn.
“Mixing doses could give us even greater flexibility for a booster program, while also helping countries who have a long way to go with their vaccine rollouts and maybe encountering supply challenges,” he says.
Two doses are required to provide complete protection and to allow the body to produce antibodies and T-cells capable of blocking and killing Covid.
The results of the Com-Cov research, which involved administering the doses four weeks apart to 850 volunteers aged 50 and up, were as follows:
AZ followed by Pfizer elicited more antibodies and T-cell responses than Pfizer followed by AZ.
Both of these combinations produced more antibodies than two doses of AZ.
Pfizer produced the strongest antibody response after two doses, while AZ followed by Pfizer produced the highest T cell response.
“We already know that both standard schedules are very effective against severe disease and hospitalizations, including against the Delta variant when given at eight to 12 weeks apart,” said lead investigator Prof Matthew Snape of the University of Oxford, adding that the findings did not undermine the UK policy of giving people the same jab twice.
Even while the interval of four weeks investigated was less than the eight to 12-week schedule most typically used in the UK, he said the new findings proved mixed dose schedules were similarly effective.
He went on to say, “This prolonged interval is known to result in a greater immunological response.”
The results of a 12-week mixed dosage trial will be released next month.
Based on the findings from the Com-Cov trial, Lead investigator Prof Matthew Snape, from the University of Oxford proposed that people who had an AstraZeneca first course might be offered the Pfizer vaccination as a booster rather of a repeat AstraZeneca and that people who got a Pfizer first course might not need an autumn booster.