AstraZeneca’s Covid-19 Vaccine: What You Need to Know
Why did the researchers test two different doses?
It was a lucky mistake. Researchers in Britain had been meaning to give volunteers the initial dose at full strength, but they made a miscalculation and accidentally gave it at half strength, Reuters reported. After discovering the error, the researchers gave each affected participant the full strength booster shot as planned about a month later.
Fewer than 2,800 volunteers got the half-strength initial dose, out of the more than 23,000 participants whose results were reported on Monday. That’s a pretty small number of participants on which to base the spectacular efficacy results — far fewer than in Pfizer’s and Moderna’s trials.
Is the AstraZeneca vaccine safe?
For years, Oxford researchers have been testing their chimpanzee adenovirus vaccine, ChAdOx1, on a number of other diseases including Ebola and Zika. Although none of those studies have reached the final, so-called Phase 3 trials, they have allowed researchers to examine the safety of the vaccine platform. The researchers have not found any serious side effects.
When the researchers adapted ChAdOx1 for Covid-19, their early clinical trials also did not turn up any adverse reactions. In Phase 3 trials, however, the testing had to be paused twice when volunteers experienced neurological problems. The Food and Drug Administration did not directly tie the vaccine to the problems, but when the agency allowed the trial to resume in the United States, it advised the company to be vigilant for any signs of similar problems.
In their announcement on Monday, AstraZeneca and Oxford said that no serious safety issues were confirmed related to the vaccine.
How much does the vaccine cost?
AstraZeneca’s vaccine has a number of advantages over other leading vaccine candidates: It’s easier to mass produce and store, and it’s also cheaper, at $3 to $4 per dose. That reflects the prices paid by governments like the United States that have placed orders for tens or even hundreds of millions of doses of the vaccine. U.S. health officials have promised that Covid-19 vaccines will be available free of charge to any American who wants one.
The Road to a Coronavirus Vaccine
Words to Know About Vaccines
Confused by the all technical terms used to describe how vaccines work and are investigated? Let us help:
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- Adverse event: A health problem that crops up in volunteers in a clinical trial of a vaccine or a drug. An adverse event isn’t always caused by the treatment tested in the trial.
- Antibody: A protein produced by the immune system that can attach to a pathogen such as the coronavirus and stop it from infecting cells.
- Approval, licensure and emergency use authorization: Drugs, vaccines and medical devices cannot be sold in the United States without gaining approval from the Food and Drug Administration, also known as licensure. After a company submits the results of clinical trials to the F.D.A. for consideration, the agency decides whether the product is safe and effective, a process that generally takes many months. If the country is facing an emergency — like a pandemic — a company may apply instead for an emergency use authorization, which…
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