What The Heck Is Happening With The AstraZeneca Vaccine?

by Elaine Roth
SOPA Images/Getty

For the past week or so, the vaccine produced by The University of Oxford, which partnered with the British-Swedish pharmaceutical company AstraZeneca, has dominated the vaccine news cycle. Unfortunately, that news hasn’t been exactly stellar. By and large, the headlines have been confusing and alarming. But as is usually the case, the headlines aren’t the full story.

How Does The AstraZeneca Vaccine Work?

Like the vaccines currently approved for emergency use in the United States, the AstraZeneca vaccine is a two-dose vaccine that focuses on the virus’s spike protein. Like those vaccines, it teaches the body’s immune system how to fight COVID. However, it uses a different method than either of the vaccines from Pfizer or Moderna.

The AstraZeneca vaccine is made from a weakened version of a common cold virus, known as an adenovirus. The adenovirus delivers a piece of COVID’s genetic code to our cells to mimic infection. Our immune system then develops an immune response to the virus, without actually being infected.

Scientists have been researching adenovirus-based vaccines for decades. In fact, an adenovirus-based vaccine was approved over the summer for Ebola, and other adenovirus-based vaccines are in clinical trial for diseases like H.I.V. and Zika.

Is The AstraZeneca Vaccine Effective?

The short story—yes.

The long story—well, it’s a bit more complicated. On March 22, AstraZeneca announced that its largest clinical trial to date, with more than 32,000 participants more than half of which had pre-existing conditions, showed that its vaccine was 79 percent effective at preventing symptomatic infections and 100 percent effective at preventing severe disease and hospitalization. By either measure, the numbers are a reason to celebrate. The celebration was cut short, however.

Hours after AstraZeneca announced the trial results, federal health officials raised questions. A group of independent medical experts responsible for overseeing the trial had concerns that AstraZeneca had presented “outdated information” that did not provide a complete view of the vaccine’s efficacy. The experts found that more current data supported an efficacy of 69–74%.

AstraZeneca replied to the concerns by noting that the 79 percent efficacy was based on early data. By late in the evening on March 24th, AstraZeneca announced that a “fuller analysis of study results” found that the vaccine was 76% effective at preventing COVID-19 with symptoms.

Some experts have said that the discrepancy might be “nothing more than a technicality.” When asked about the AstraZeneca vaccine, Fauci said on “Good Morning America” that “this is very likely a very good vaccine.” He also pointed out that the medical experts’ concerns were an example of the many safeguards in place to ensure the quality of vaccines.

Does The AstraZeneca Vaccine Cause Blood Clots?

In early March, European countries temporarily halted their rollout of the AstraZeneca vaccine after a small number of recently vaccinated folks reported an extremely rare form of blood clot–cerebral sinus vein thrombosis (CSVT)–in the brain, according to the BBC. Of the 11 million folks who received the vaccine in the UK, five cases were reported. Another thirteen were reported to the European Medicines Agency (EMA)

The recently completed U.S. trial found no safety concerns regarding blood clots, even after a specific review was performed. Likewise, after conducting its own review, European regulators concluded that the vaccine is “safe and effective vaccine.” A label will be added to the vaccine to alert healthcare workers about the very rare complication, but ultimately, officials are confident that the benefits of vaccination far outweigh the very small potential risk.

Does The AstraZeneca Vaccine Protect Against Variants?

The big question around vaccinations is with respect to how effective they are against the variants now circulating in many parts of the world. The answer is more complicated than a simple yes or no.

Early analysis from one UK trial found that the AstraZeneca vaccine provided a similar level of protection against the variant originally identified in the UK as it did against the original virus. That’s great news.

Against the variant first identified in South Africa, the AstraZeneca vaccine fared less well. A study of 2,000 adults younger than 65 found that the AstraZeneca vaccine offered limited protection against mild to moderate COVID. (South Africa has since temporarily suspended its roll-out of the AstraZeneca vaccine.)

Why Do We Need Another Vaccine, Anyway?

Federal officials believe that by the end of May, Pfizer, Moderna, and Johnson & Johnson will produce enough vaccine doses to cover every American adult. If that proves true, we probably don’t need another vaccine.

But we (as in the United States) do not live in a vacuum. The world does need this vaccine. “The world, the species, depends on this vaccine. This is 2.5 billion people’s worth of vaccine,” says Eric Topol, a physician-scientist and director of the Scripps Research Translational Institute in La Jolla, California, in an interview with Nature.

The AstraZeneca vaccine is easier to store than either Pfizer and Moderna—requiring nothing but an ordinary refrigerator. It’s also inexpensive to produce, costing only “a few dollars per dose.”

“[I]n many countries, especially on the African continent, the AstraZeneca vaccine is the only one that will be available in substantial quantities,” says Shabir Madhi, a vaccinologist at the University of the Witwatersrand in Johannesburg, South Africa in an interview with Nature. Which means: yes, we (a collective, global we) do need this vaccine.

Vaccines are our light at the end of this pandemic tunnel. The more vaccines we can manufacture and distribute globally, the faster we can stop this pandemic and return to whatever version of normal awaits on the other side.

Information about COVID-19 is rapidly changing, and Scary Mommy is committed to providing the most recent data in our coverage. With news being updated so frequently, some of the information in this story may have changed after publication. For this reason, we are encouraging readers to use online resources from local public health departments, the Centers for Disease Control, and the World Health Organization to remain as informed as possible.