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TO A FEW MONTHS Long 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 rejecting the AstraZeneca jab, preferring to wait for Pfizer or Moderna.
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These preferences are derived from the results of clinical trials. Moderna and Pfizer, which make the same type of vaccine, reported an efficacy of 94-95%, while Johnson & Johnson and AstraZeneca reported 63-66%. Emmanuel Macron, president of France, has slandered the AstraZeneca jab as “almost ineffective” in older patients.
However, the reported efficacy gap may say more about the trials than it does about the vaccines themselves. Some studies counted people with mild symptoms as positive; others don’t. Those with the lowest reported efficacy used participants in countries where partially immune-resistant variants of SARS–CtheV-2 are common. One tried only a single dose regimen.
Fortunately, apple-to-apple comparisons are now possible, based on millions of people who received different vaccines in the same country at the same time. And recent data from Britain, hitting 20 million people by Pfizer or AstraZeneca, paints a different picture of the trial results. Three studies show that single doses of the two jabs are equally effective.
The last paper, a preprint for the Lancet published on March 3, found that one dose of either injection protects 80% against hospitalization in people at least 80 years old, beginning 14 days after vaccination. Another study, in Scotland, included younger age groups and also found that the two strokes had similar potency against hospitalization.
For a virus looking for new hosts, this is bad news, which will only get worse. Few people in Britain have received second doses. However, Israel has almost completed a two-dose mass vaccination program using the Pfizer vaccine. According to the latest data from Israel, two doses protect 90% against any form of covid-19, including asymptomatic infection.
Pfizer jab is expensive and must be stored in freezers. In contrast, AstraZeneca is cheap and only needs normal refrigeration. If the AstraZeneca vaccine also matches Pfizer’s efficacy, which now seems likely, it could play a leadership role in ending the pandemic, as long as people don’t reject it based on ill-founded blows from people like Macron.■
Sources: “BNT162b2 mRNA covid-19 vaccine in a nationwide mass vaccination setting,” by N. Dagan et al., 2021; studies by Public Health England and Public Health Scotland; company press releases; The Economist
This article appeared in the graphic details section of the print edition under the title “Six of One.”
