A third candidate vaccine is also extremely effective against COVID-19, confirming that previous results were not a fluke and that vaccination offers a way out of the pandemic.
AstraZeneca and Oxford University's vaccine, which uses a different technology but the same target as two other candidates, is clearly as effective, according to a press release from the collaborators on Monday.
Using a lower-dose first shot, which conserves the vaccine, and then a full-dose second shot provided protection about 90% of the time, the company and university found.
Both Pfizer and its German collaborator BioNTech and Moderna showed earlier this month that their candidate vaccines can protect against COVID-19 symptoms 95% of the time.
"November 2020 looks set to be the month that humanity developed the tools to turn the tide against this devastating virus," Professor Peter Piot, Director of the London School of Hygiene & Tropical Medicine, said Monday in a prepared statement.
These three are among six candidate vaccines being supported by more than $10 billion in U.S taxpayer dollars. The government is also supporting an experimental vaccine from Sanofi/GSK and one from startup Novavax, which are expected to begin large trials in the U.S. in the coming weeks. Merck, which has received far less funding, is a few months further behind.
Here’s what we know about all three vaccine trials and what they might mean for the future of the pandemic.
What are the leading COVID-19 candidate vaccines?
Pfizer and the German biotechnology company BioNTech developed one of the candidate vaccines, BNT162b2, and showed it was 95% effective in protecting against symptomatic COVID-19.
Moderna, a Cambridge, Massachusetts-based biotechnology company, released data early Monday on its candidate vaccine, mRNA-1273, which was developed in collaboration with the U.S. government. Moderna's 95% effectiveness results are considered interim, with final results expected any day.
AstraZeneca collaborated with Oxford University to produce its vaccine, called AZD1222. On Monday, the pair released interim results from trials in the U.K. and Brazil, showing the vaccine could be 90% effective if delivered in a specific way.
How effective are the candidate vaccines and what does that mean?
All of the late-stage vaccine trials include at least 30,000 volunteers, half of whom receive the active vaccine and half the placebo.
Most of the vaccines at this stage require two doses to become maximally effective. The Pfizer/BioNTech shots are being given 21 days apart, Moderna's are given 28 days apart, and AstraZeneca/Oxford's about a month apart.
Beginning a week after the second dose, participants are watched to see whether they come down with COVID-19.
In each of the studies, after about 150 participants have developed COVID-19, it is statistically possible to determine the vaccine's effectiveness.
In the Moderna trial, 90 of the first 95 participants to develop COVID-19 had received the placebo and only five the active vaccine, so it was 94.5% effective. Results from another 56 participants are expected shortly.
Pfizer/BioNTech, whose trial is about a week ahead of Moderna's, reported on Nov. 18 that of 170 confirmed cases of COVID-19 among its trial participants, 162 were in the placebo group versus eight in the vaccine group.
On Monday, AstraZeneca/Oxford reported that of 131 participants who developed COVID-19, 70% overall were protected.
But when they examined two different ways of delivering the vaccine, they found that one regimen was substantially more effective. In a trial in Brazil with 10,300, participants were given two equal doses of the vaccine and were about 60% protected, while in a U.K. trial of 12,400, participants were given a low-dose first shot and a regular-dose second shot and were shown to be 90% protected.
Are there any side effects to the vaccines?
Most people who get a COVID-19 vaccine will endure side effects, particularly after a second dose. All three candidate vaccines reported mild or moderate side effects, mostly pain at the injection site, fatigue and aching muscles and joints for a day or two.
“A sore arm and feeling crummy for a day or two is a lot better than COVID,” said Dr. William Schaffner, professor of health policy and of preventive medicine at the Vanderbilt University School of Medicine.
What difference are there between the candidate vaccines?
Most of the U.S.-backed vaccines target the so-called "spike protein" found on the surface of the virus that causes COVID-19, which allows the virus to attach itself to host cells and infect them.
All three of these candidate vaccines work by presenting this spike protein to the immune system. The spike proteins aren’t dangerous because the rest of the virus isn’t present, however, the body now sees the protein and designs immune soldiers to fight it upon future exposure.
The Moderna and Pfizer vaccines deliver strands of genetic material known as mRNA, which turns people’s cells into spike protein factories.
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This technology has never been used before in an approved vaccine, though it has been tested against other diseases. The mRNA technology was chosen this time because scientists knew it could be developed quickly.
The AstraZeneca vaccine uses a modified cold virus found in chimpanzees and weakened, so it cannot cause illness in people. This virus delivers the spike protein's genetic material.
Other COVID-19 vaccine candidates being supported by the U.S. government target the spike protein via a different carrier virus or tiny particle.
The three most advanced vaccines all require different types of storage.
The Pfizer/BioNTech vaccine must be kept super-cold – at the temperature of dry ice – until shortly before it is used, while the Moderna vaccine needs to be frozen if stored for a long time, but it can be refrigerated for up to a month before being used. The AstraZeneca/Oxford vaccine can be kept refrigerated throughout, which should make it easier to deliver to areas that do not have easy access to freezers.
When can I get a COVID-19 vaccine?
Before the companies can apply to the U.S. Food and Drug Administration for authorization to provide their vaccine to the public, they must clear several hurdles.
All three have made it past the first: showing that they are at least 50% effective.
The second hurdle concerns safety. About half the trial participants must be two months past their second shot to prove that the candidate vaccines are safe. If someone were to develop a severe vaccine reaction, that would likely to happen within six weeks of getting the shot.
So far, no one in the Pfizer/BioNTech or Moderna trials has suffered a severe reaction. Pfizer has passed the half-way point, while Moderna, which slowed down its recruitment to ensure a diverse pool of participants, is expected to pass it within days.
Two people in an AstraZeneca/Oxford trial did have severe reactions after being vaccinated, and trials were stopped for several weeks while those cases were investigated, but they were then allowed to resume.
AstraZeneca/Oxford said Monday that they have a safety database from over 24,000 participants in clinical trials in the U.K., Brazil and South Africa, with follow-up since April. It's not clear whether the FDA would require safety data solely from the pair's U.S. trial.
The final hurdle concerns production. All companies have to show that they can safely produce their vaccine at scale. Pfizer, which already submitted an application to the FDA for authorization, has completed this work and Moderna is expected to do so shortly.
Finally, the FDA will take some time to review each application, as will an independent committee, which is scheduled to meet on Dec. 10.
President Donald Trump has promised that vaccine would be distributed within 24 hours of an FDA authorization. It would first go to front-line health care workers.
Moderna said recently it will have 20 million doses available by the end of this calendar year and another 500 million to 1 billion next year. Pfizer has said it will have as much as 50 million doses of its vaccine manufactured by the end of this year, and another 1.3 billion next year.
Both companies have agreed to provide Americans with 100 million doses apiece, already funded through federal support of manufacturing and distribution.
Moderna has received nearly $2.5 billion from U.S. taxpayers to develop, manufacture and distribute its vaccine; while Pfizer/BioNTech has been promised just under $2 billion for manufacturing and distribution of the first 100 million doses, with an option to buy an additional 500 million doses.
AstraZeneca/Oxford, which said it has ongoing large-scale manufacturing in over 10 countries to support equitable global access, has been promised $1.3 billion in U.S. funding to provide 300 million doses of its vaccine.
The pair have agreed to supply their vaccine on a not-for-profit basis for the duration of the pandemic and in perpetuity to low- and middle-income countries.
While the companies are expected to start delivering vaccine as soon as they win FDA authorization, the vaccines will be rolled out first to front-line health care workers, then nursing home residents and first responders and then other vulnerable people. The general public will probably get its first access to a vaccine in April or May of 2021.
Follow Adrianna Rodriguez and Karen Weintraub on Twitter: @AdriannaUSAT @kweintraub
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.
This article originally appeared on USA TODAY: COVID vaccine from Moderna, Pfizer, AstraZeneca: What's the difference