A second, better, vaccine against covid-19 arrives

A second, better, vaccine against covid-19 arrives

And there are surely more to come

WAITING FOR a breakthrough in the fight against covid-19 has been a bit like waiting for a bus to arrive. After a year of watch-checking and neck-craning, two come along at once. Just a week apart, successful results from a pair of vaccines have been reported. An announcement on November 16th, by Moderna, an American biotech firm, followed that of Pfizer and BioNTech on November 9th. Both vaccines will improve humanity’s lot. But there are important differences between the two.

Moderna says that its offering is 94.5% effective. Stockmarkets celebrated, just as they had when Pfizer declared its result. American share indices closed at record highs. Moderna’s estimate of efficacy is based on an interim study of a trial of 30,000 patients—ie, the researchers took a peek at the data gathered in the ongoing trial. They found that 95 participants had caught covid-19, of whom 90 were in the placebo arm and thus had received dummy vaccinations rather than the real thing.

This is just ahead of Pfizer’s efficacy of 90%-plus (although both firms’ estimates are likely to be adjusted when complete data are available). Even if they are adjusted downwards this will not alter the fact that the world now has two highly effective covid-19 vaccines on its hands. (Most observers had not dared hope for a figure above 70%.)