On Monday, AstraZeneca announced that its coronavirus vaccine is up to 90% effective, according to late-stage trials. It’s also relatively cheap and easy to store, meaning it may become the choice vaccine for developing nations.
Though the vaccine’s efficacy was 90% in one of the dosing regimens its team tested, its average effectiveness was 70%. A vaccine’s efficacy is measured as the percent reduction in disease incidence among a vaccinated group of people compared to an unvaccinated or placebo group, according to the Canadian Center of Vaccinology. (The average flu vaccine is about 31-44% effective, the CDC reports.)
The team administered different vaccine regimens to different groups: One received two full doses, whereas another received a half dose followed by a full dose. The team expected that two high doses would set off the strongest immune response, Andrew Pollard, director of the Oxford University Vaccine Group and chief investigator for the trial, explained at a news conference. But the opposite occurred.
For the subgroup that received two full doses of the AstraZeneca vaccine a month apart, it was only 62% effective. But in the group that was given half a dose followed by a full dose one month later, the vaccine was 90% effective.
Oxford scientists, who helped develop the new vaccine, are positing that a half dose followed by a full dose may prime the body to create a greater immune response to SARS-CoV-2, the virus that causes COVID-19. But they’re unsure why. The 90% efficacy rate, while comparable to 95% effectiveness reported last week by both Moderna and Pfizer, was recorded in a group of fewer than 3,000 people. Conversely, Moderna’s trial has involved 30,000 people, half of whom received its vaccine and half a placebo. Pfizer’s trial has enrolled more than 43,000 volunteers, 38,955 of whom have completed its vaccine regimen as of November 16 (with half receiving a vaccine and half a placebo).
AstraZeneca’s results reported Monday come from trials involving a total of 23,000 people in the U.K. and Brazil, 11,636 of whom were given the vaccine with the remaining receiving a placebo. Researchers said 131 Covid-19 cases were detected during the clinical trials and none of the study participants that fell ill required hospitalization. AstraZeneca has yet to release information on how many of these participants received the vaccine and how many received the placebo.
Unlike Pfizer and Moderna’s mRNA vaccines, which use synthetic genetic material to help the body produce one small component of the virus itself that the immune system can learn from—in this case, SARS-CoV-2’s iconic spike protein—the AstraZeneca vaccine uses a weakened version of a common cold virus that’s combined with genetic material for the spike protein, Danica Kirka writes for the Associated Press. “After vaccination, the spike protein primes the immune system to attack the virus if it later infects the body.”
Watch to learn more about mRNA vaccine technology:
And while Moderna and Pfizer and BioNTech’s vaccines need to be stored at freezing temperatures, this new vaccine remains viable at 36 to 46 F. (Storing vaccines at their required temperature is one of the greatest challenges that developing countries face with routine immunization.)
“I think these are really exciting results,” Pollard said. “Because the vaccine can be stored at fridge temperatures, it can be distributed around the world using the normal immunization distribution system.”
It’s also cheaper. Pfizer and BioNTech, as part of their $1.95 billion contract with the federal government under Operation Warp Speed, “have set the initial price at $19.50 a dose, which comes to $39 per patient (since each vaccine requires a two-dose regimen),” Katie Jennings writes for Forbes. Moderna, which received nearly $1 billion from the Biomedical Advanced Research and Development Authority and has a $1.5 billion contract for 100 million doses, says its vaccine will cost approximately $25 a dose or $50 a patient, since it too requires a second dose.
Conversely, AstraZeneca’s vaccine will cost about $2.50 a dose.
AstraZeneca has pledged to not make a profit on the vaccine during the pandemic and having reached agreements with governments and health organizations, Kirka reports.
It plans to have more than 300 million full doses of its vaccine available globally by the end of March 2021. That number could increase by 50%, given the promising results of first administering a half dose to patients, followed by a full dose one month later. The company hopes to produce around 200 million doses a month, AstraZeneca’s Executive Vice President Pam Cheng said during a press event.
The Pfizer, Moderna, and AstraZeneca vaccines will all need to be approved by regulators before they can be widely distributed. “AstraZeneca said it will immediately apply for early approval of the vaccine where possible, and it will seek an emergency use listing from the World Health Organization, so it can make the vaccine available in low-income countries,” Kirka writes.
Pfizer and Moderna plan to apply for FDA emergency use authorization this month. Moderna stated on November 16 that it expects to be able to ship about 20 million vaccine doses in the U.S. by the end of this year and another 500 million to 1 billion in 2021, if authorized to do so. Pfizer expects to produce up to 50 million vaccine doses in 2020, and 1.3 billion in 2021, if authorized.
These COVID-19 vaccine rollout plans raise the question: Who should—and ultimately will—get vaccinated the soonest?
Vaccine supplies will be limited at first, meaning the decisions about who gets those first doses could save tens of thousands of lives, Jill Neimark writes for Undark Magazine. “The consensus among most [disease] modelers is that if the main goal is to slash mortality rates, officials must prioritize vaccinating those who are older, and if they want to slow transmission, they must target younger adults,” she writes.
Many experts agree that the threat of superspreaders must not be ignored. “This is a pandemic defined by clusters,” Christopher Cox writes for WIRED. “Some cause deadly outbreaks in nursing homes, prisons, and meatpacking plants. Others overwhelm families and friend groups. Although the numbers vary from study to study, SARS-CoV-2 seems to follow the 80/20 rule: 80 percent of cases stem from just 20 percent of infected individuals.” Some network theorists believe that social butterflies, who are the most likely to become superspreaders, should be vaccinated first.
For now, it seems, the first doses of a COVID-19 vaccine will go to health care providers here in the U.S. and in the World Health Organization’s member countries, per its recommendation. But the CDC committee is grappling with a fundamental question, Cox writes: Do doctors first immunize the most vulnerable, and therefore protect individuals, or do they immunize the most social, and therefore reduce transmission and protect the population?
And then, of course, are the issues of trust and inequity, Neimark writes: “For instance, it’s widely acknowledged that Black people have experienced hospitalization and death at disproportionately high rates compared to White people.” And because of algorithmic bias, a recent study found, White patients are often prioritized over Black patients in hospitals, even when Black patients are sicker than their White counterparts. “When ethicists begin to talk about prioritizing Black people for vaccines, it can be perceived as an intent to experiment on them by pushing them to the head of the line,” Neimark writes.
One thing is sure: Multiple vaccines will be necessary to help bring an end to the pandemic, which has to date sickened more than 12.5 million Americans and nearly 60 million people worldwide. And if there’s any silver lining to the surge of cases in the U.S. and worldwide, Rebecca Robbins reports for the New York Times, it’s that the uptick could make results from other closely watched vaccine trials available sooner and with greater statistical power, while also speeding up trials of COVID-19 treatments.