Covid-19: Third vaccine dose boosts immune response but may not be needed, say researchers

The interval between the first and second doses of the Oxford AstraZeneca vaccine can be extended up to 10 months and a third dose of the vaccine provides a strong boost to the immune response, according to preliminary results.

In a preprint, published on 28 June,1 researchers from the University of Oxford reported that extending the interval between the first and second dose to 45 weeks resulted in higher antibody titres. They also found that a third dose given 44 to 45 weeks after the second increased antibody titres further, and that adverse events were lower after the second or third dose than after the first.

Researchers said the results are positive, especially for areas affected by vaccine shortages, as they could provide “greater flexibility in vaccination schedules.” But they said that currently there is no …