The European Medicines Agency (EMA) has urged health authorities to give out second Covid-19 vaccine doses as soon as possible, and consider mixing and matching vaccines to increase people’s protection from the rapidly spreading Delta variant.
People who have received one dose of AstraZeneca are particularly vulnerable to the Delta variant which was first detected in India and is rapidly spreading in Britain, said EMA head of vaccine strategy Marco Cavaleri.
They should be given second doses as soon as possible – and health authorities could choose to give them doses of Pfizer or Moderna instead, he said.
“A second dose would increase the protection quite significantly,” said Dr Cavaleri in response to a question from The Irish Times.
“Considering that the protection after the first dose is a bit lower than what we see with the Alpha [British] variant . . . it will be important to see if the interval between the two doses could be shortened.”
Data from the United Kingdom has shown that two doses of the AstraZeneca vaccine offers strong protection from the Delta variant, but that people who have had only one shot are particularly vulnerable to infection from the new strain.
Spread of the more infectious strain is causing alarm as large numbers of people in vulnerable age groups remain exposed, particularly those who received AstraZeneca doses as the vaccine has a lengthy interval period until the second shot of eight to 12 weeks.
Better immune response
Health authorities could consider “mixing and matching” vaccines to give people mRNA jabs instead of a second dose of AstraZeneca, said Dr Cavaleri.
“This approach . . . has been proven successful in the past in the context of the use of other vaccines. It is well known that mixing and matching vaccines often ends up in a better immune response,” said Dr Cavaleri.
“We have so far limited evidence with respect to the Covid-19 vaccine about the option of mixing and matching them. But some preliminary studies have shown that indeed the immune response seems to be satisfactory, and no particular issues were emerging from a safety perspective. So it looks like it could be a strategy that could be employed,” he said.
He added that it would be a decision for national authorities in each country to make.
“It’s up to them. It’s up to them to decide whether they want to use the vaccine giving two doses of Vaxzevria [AstraZeneca] , or whether they prefer for a number of reasons to give a second dose of messenger RNA,” said Dr Cavaleri.
“As I said, all the evidence that we have so far is that [is] not going to be problematic.”
