FILE PHOTO: AstraZeneca vaccination in southern Spain
AstraZeneca vaccination in southern Spain, March 25, 2021.

The world's most widely distributed COVID-19 vaccine is back in the news, and not for a good reason.

AstraZeneca drew an unusual public rebuke from U.S. officials this week for overstating the results of a clinical trial.

While those officials expressed confidence overall in the vaccine, it's the latest in a series of missteps for a critical tool for ending the pandemic.

>AstraZeneca's vaccine is the backbone of the global effort to immunize lower-income countries. Experts are concerned that confidence in the shot has slipped unnecessarily following a string of self-inflicted wounds, unproven safety scares and discouraging but limited efficacy results.

Red flag

The company announced Monday that the vaccine was 79% effective in preventing any symptoms of COVID-19 and 100% effective against severe illness and hospitalization. Those results come from a clinical trial involving more than 32,000 people in the United States, Peru and Chile.

But late that night, the clinical trial's independent oversight board waved a red flag. It said the company was using "outdated information" that gave an "incomplete view" of the vaccine's efficacy, according to a statement from the National Institute of Allergy and Infectious Diseases (NIAID).

COVID-19 vaccination in Dhaka, March 24, 2021.

The company's announcement "might in fact be misleading a bit,” NIAID Director Anthony Fauci said on the ABC News program “Good Morning America” on Tuesday.

With more recent cases taken into account, the efficacy data slips to between 69% and 75%, according to The Washington Post, which obtained the letter from the oversight board.

Those are still strong results, Fauci told reporters Wednesday.

"At the end of the day, when you look at the data, this is going to turn out to be a good vaccine," he said.

But Fauci conceded that the lack of transparency is likely to undermine confidence in the vaccine.

In demand

The vaccine was first developed by researchers at the University of Oxford. AstraZeneca signed on last April to shepherd it through clinical trials and do large-scale manufacturing.

AstraZeneca has secured orders for more than 3 billion doses, according to Bloomberg, more than double the demand for any other shot.

At $3 to $4 per dose, it is cheaper than other vaccines. And it can be stored at refrigerator temperatures, rather than the extreme cold that some other vaccines require.

Those traits have made it a popular choice for COVAX, the World Health Organization-backed program aimed at more equitable vaccine access. COVAX announced it is delivering 237 million doses of the AstraZeneca vaccine in February and March to 142 countries.

The only other shots currently available in the program are 1.2 million doses of the Pfizer-BioNTech vaccine.

Clinical trial paused

AstraZeneca's trouble in the United States was not the first time the company raised eyebrows with U.S. officials. The company did not inform them when it paused a worldwide clinical trial last September to investigate a possible bad neurological reaction to the vaccine. A review later cleared the shot.

That clinical trial raised eyebrows for other reasons.

Due to a manufacturing mix-up, some participants got half the expected dose in their first shot of the two-shot vaccine.

Unexpectedly, that dosage worked better. Two full-strength shots were 62% effective, while one half-strength and one full-strength dose were 90%.

The researchers have not explained why, and other scientists are puzzled.

False alarm

While critics say those errors were avoidable, the vaccine has also suffered from a recent false alarm over its safety.

Several countries put the shot on hold earlier this month after blood clots or bleeding disorders developed in a small number of people following vaccination — 25 cases out of 20 million people vaccinated, according to the European Medicines Agency (EMA).

The timing may have been coincidental, and regulators called the temporary halts "precautionary."

Critics said halting vaccination based on such weak evidence in the face of a deadly pandemic was a bad idea and would likely erode confidence in it.

A dose of AstraZeneca vaccine is prepared at COVID-19 vaccination centre in the Odeon Luxe Cinema in Maidstone, Britain…
Experts Question AstraZeneca Vaccine Pause
Real benefits of COVID-19 prevention outweigh unproven risks of blood clots, experts say

British and EU regulators reviewed the evidence and continued to recommend the shot. In a statement last Thursday, EMA said "the vaccine’s proven efficacy in preventing hospitalization and death from COVID-19 outweighs the extremely small likelihood" of blood-clotting.

Effective, but not everywhere

While authorities vouch for its safety, the vaccine's efficacy suffered a setback in South Africa in February.

The shot was only 10% effective against mild to moderate cases of COVID-19 caused by a new variant of the virus that had become dominant in the country.

The South African government stopped the rollout of the vaccine to health care workers shortly after it began. It switched to the Johnson & Johnson vaccine and has since sold its doses to other African Union countries.

Real-world data paints a much rosier picture than the string of stumbles suggests. In a study in Britain, the risk of hospitalization fell 94% after just one shot. The research has not yet been reviewed by other experts.

Plus, the vaccine looks to be much more potent against a variant first spotted in Brazil compared to the South African variant, according to another study awaiting peer review.

The company's problems have officials worried that people will lose confidence in an important vaccine that experts say can play an important role in taming the pandemic. NIAID's Fauci told reporters Wednesday that U.S. regulators will go over all the data carefully and present it all publicly before approving the shot in this country.

"At the end of the day, everything is going to be open and transparent," he said, "and hopefully, that will dispel any hesitancy that was associated with this little bump in the road."

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