Six of one – New data show that leading covid-19 vaccines have similarly high efficacy | Graphic detail
A FEW MONTHS ago the biggest question about covid-19 vaccines was whether any of them would work. Today the problem in some countries is having too many to choose from. In Europe some people are spurning AstraZeneca’s jab, preferring to wait for Pfizer’s or Moderna’s instead.
Such preferences stem from the results of clinical trials. Moderna and Pfizer, which make the same type of vaccine, announced an efficacy of 94-95%, whereas Johnson & Johnson and AstraZeneca reported 63-66%. Emmanuel Macron, France’s president, has maligned AstraZeneca’s jab as “quasi-ineffective” in older patients.
However, the gap in reported efficacy may say more about the trials than about the vaccines themselves. Some studies counted people with mild symptoms as positive cases; others did not. Those with lower reported efficacy used participants in countries where partly immune-resistant variants of SARS–CoV-2 are common. One tested only a single-dose regimen.
Fortunately, apples-to-apples comparisons are now possible, based on millions of people who got different vaccines in the same country at the same time. And recent data from Britain, which has given either Pfizer’s or AstraZeneca’s jabs to 20m people, paint a different picture from the trial results. Three studies show that single doses of the two jabs are similarly effective.
The latest paper, a preprint for the Lancet published on March 3rd, found that one dose of either jab is 80% protective against hospitalisation in people aged at least 80, starting 14 days after vaccination. Another study, in Scotland, included younger age groups and also found the two jabs had similar potency against hospitalisation.
For a virus seeking new hosts, this is bad news—which will only get worse. Few people in Britain have received second doses. However, Israel has almost finished a two-dose mass-vaccination programme using the Pfizer vaccine. According to the latest data from Israel, two doses are about 90% protective against any form of covid-19, including asymptomatic infection.
Pfizer’s jab is pricey and must be stored in freezers. In contrast, AstraZeneca’s is cheap and needs only normal refrigeration. If the AstraZeneca vaccine also matches Pfizer’s efficacy, which now appears likely, it could play a leading role in ending the pandemic—so long as people do not reject it based on ill-founded swipes from the likes of Mr Macron.■
Sources: “BNT162b2 mRNA covid-19 vaccine in a nationwide mass vaccination setting”, by N. Dagan et al., 2021; studies run by Public Health England and Public Health Scotland; company press releases; The Economist
This article appeared in the Graphic detail section of the print edition under the headline “Six of one”