London: The delayed second and third doses of the AstraZeneca vaccine boost immunity against Covid-19, according to a study.
The study by Oxford University, which developed the jab with the British-Swedish firm, said an interval of up to 45 weeks between the first and second dose of the AstraZeneca vaccine led to an enhanced immune response rather than compromising immunity.
The study added giving a third dose of the jab more than six months after the second dose also leads to a “substantial increase” in antibodies and induces a “strong boost” to subjects' immune response.
“This should come as reassuring news to countries with lower supplies of the vaccine, who may be concerned about delays in providing second doses to their populations,” Agence France-Presse quoted Andrew Pollard, the lead investigator of the Oxford trial, as saying.
“There is an excellent response to a second dose, even after a 10-month delay from the first,” he added.
The results for a delayed AstraZeneca third dose were positive particularly as nations with advanced vaccination programmes consider whether third booster shots will be required to prolong immunity, the researchers said.
“It is not known if booster jabs will be needed due to waning immunity or to augment immunity against variants of concern,” Teresa Lambe, the study's lead senior author, said.
Explaining the research showed the AstraZeneca jab “is well tolerated and significantly boosts the antibody response”, Lambe said the results were encouraging “if we find that a third dose is needed”.
The study indicated that the vaccine’s side effects in general were “well tolerated” with “lower incidents of side effects after second and third doses than after first doses”.