Delayed doses of AstraZeneca vaccine boost immunity: Study

LONDON: Delayed second and third doses of the AstraZeneca vaccine boost immunity against COVID-19, a study by Oxford University, which developed the jab with the British-Swedish firm, said on Monday. 

According to the study, 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.

“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”, said the pre-print study, meaning that it has yet to be peer-reviewed.

Meanwhile, lead investigator of the Oxford trial, Andrew Pollard, said, “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.”

“There is an excellent response to a second dose, even after a 10-month delay from the first,” he added.  The researchers said 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.

“It is not known if booster jabs will be needed due to waning immunity or to augment immunity against variants of concern,” said the study’s lead senior author, Teresa Lambe.

She explained the research showed the AstraZeneca jab is well tolerated and significantly boosts the antibody response. Lambe added results were encouraging “if we find that a third dose is needed”.

A number of nations have suspended the use of the vaccine as a result or restricted its use by younger groups who are less at risk from COVID. The Oxford study indicated that side effects from the vaccine in general were “well tolerated” with “lower incidents of side effects after second and third doses than after first doses”.