Inject a vaccine against covid-19 Pfizer/BioNTech after another of AstraZeneca/Oxford, and spacing the two doses of the latter by several months substantially improves the immunity, according to two preliminary studies published Monday by the University of Oxford.
The researchers claimed to show that, far from diminishing the efficacy of the vaccine, an interval of up to 45 weeks between the two required doses of AstraZeneca / Oxford improves the immune response to the virus.
“This should be reassuring news for countries with fewer vaccine supplies, which may be concerned about delays in obtaining second doses,” said the professor. Andrew Pollard, director of the Oxford Vaccine Group, which developed the vaccine together with the Anglo-Swedish pharmaceutical group AstraZeneca.
“There is an excellent response to the second dose even 10 months after receiving the first,” he stressed.
Another study from the same university published in February by the prestigious scientific journal The Lancet it already indicated that the efficacy of the vaccine was greater with a three-month interval between doses (81%) than with a six-week interval (55%).
As a result of this new research, the scientists also discovered that a third dose injected more than six months after the second leads to a “significant increase” in antibodies and causes a “strong increase” in the immune response against the covid-19, even against known variants of the coronavirus.
“We do not know whether booster injections will be needed due to decreased immunity or to increase immunity against variants,” said Teresa Lambe, lead author of the study. But he noted that the research shows that a third dose of the vaccine “is well tolerated and significantly increases the response to the level of antibodies.”
“It is very encouraging news if a third dose is found to be necessary,” he added.
Combine different vaccines
The researchers also claim that the vaccine caused “fewer side effects after the second and third doses than after the first.”
The vaccine AstraZeneca, which uses a technology called “viral vectors” (adenovirus), has raised concern after a link was established between its administration and the development of rare but sometimes fatal thrombi.
As a result, many countries restricted its use to older people and some stopped using it.
In a separate study also published Monday, the University of Oxford also found that combining doses of AstraZeneca/Oxford and its German-American competitor Pfizer/BioNTech, injected four weeks apart, also improves the immune response against covid-19.
Efficacy varies, however, according to the order, according to this study that found that one dose of AstraZeneca / Oxford followed by another of Pfizer / BioNTech generates a “better immune response” than the reverse.
Results for a 12 week interval between the two doses will be available shortly and “They will be instrumental in deciding the future of the UK vaccination program”said Professor Jonathan Van-Tam, England’s deputy chief medical officer.
The combination of two different sera “could give us even more flexibility,” he said.
In the UK, 84.1% of the adult population have received a first injection and 61.6% the full regimen.