Halfdose vaccine succeeds by ‘mistake’

LONDON: It took Oxford University’s brightest minds decades of work to give them the expertise to develop a Covid19 vaccine. In the end, it was a momentary error — and a dose of good fortune — that carried them over the line.

The Oxford vaccinologists were exhilarated on Monday when drugmaker AstraZeneca, with whom they developed the shot, announced that it could be about 90% effective, citing data from latestage trials.

‘‘It can only happen if extraordinary support is provided,’’

Adrian Hill, director of Oxford University’s Jenner Institute which developed the shot, said.

‘‘We had pretty well the whole institute in Oxford working on this vaccine.’’

While skill and hard work drove development, AstraZeneca said it was a minor mistake that made the team realise how they could significantly boost the shot’s success rate, to as much as 90% from around 60%: by administering a half dose, followed by a full dose a month later.

‘‘The reason we had the half dose is serendipity,’’ Mene Pangalos, head of AstraZeneca’s nononcology research and development, said.

The plan was for trial participants in Britain to receive two full doses, but researchers were perplexed when they noticed that side effects, such as fatigue, headaches or arm aches were milder than expected, Pangalos said.

‘‘So we went back and checked . . . and we found out that they had underpredicted [miscalculated] the dose of the vaccine by half.’’

He said the team nonetheless decided to press ahead with that halfdose group, and to administer the second, full dose booster shot at the scheduled time.

The results showed the vaccine was 90% effective among this group, while a larger group who had received two full doses produced an efficacy readout of 62%, Pangalos said.

‘‘Yes, it was a mistake.’’