Latest Results Show Pfizer COVID-19 Vaccine is Safe and 95 Percent Effective

The drug maker expects to produce up to 50 million vaccine doses in 2020 and up to 1.3 billion doses in 2021.

scientist vaccinating man

Medically reviewed in December 2020

Updated on November 18, 2020

Pfizer and the German drugmaker, BioNTech, announced the first set of complete results from their ongoing coronavirus vaccine trial. The results suggests it’s 95 percent effective against COVID-19, starting 28 days after the first dose.

The results were based on an evaluated of 170 confirmed cases of COVID-19 with 162 observed in the placebo group compared to 8 in the vaccine group.

The effectiveness of the vaccine was similar for both men and women and people of different races and ethnicities.

For adults older than 65, the vaccine was shown to be 94 percent effective.

No serious safety concerns have been reported.

“The study results mark an important step in this historic eight-month journey to bring forward a vaccine capable of helping to end this devastating pandemic. We continue to move at the speed of science to compile all the data collected thus far and share with regulators around the world,” said Albert Bourla, DVM, Ph.D. Pfizer chairman and CEO in a November 18 news release. “With hundreds of thousands of people around the globe infected every day, we urgently need to get a safe and effective vaccine to the world.”

The next steps
The Phase 3 clinical trial of the experimental vaccine, known as BNT162b2, began on July 27. To date, 43,661 participants have enrolled. Of these participants, 42 percent have diverse backgrounds.

As of November 13, 41,135 have already received a second dose of the vaccine.

The November 18 announcement follows an earlier independent review of the Phase 3 trial data. The analysis was conducted on November 8 by an external, independent Data Monitoring Committee. At that time, the committee review found that the Pfizer/ BioNTech vaccine has an efficacy rate greater than 90 percent at seven days after the second dose.

Now, following these latest results, Pfizer says that within days it will ask the U.S. Food and Drug Administration (FDA) for Emergency Use Authorization (EUA) of the two-dose vaccine.

The drug maker expects to produce up to 50 million vaccine doses in 2020 and up to 1.3 billion doses in 2021.

More about the vaccine
The Pfizer/ BioNTech vaccine candidate, BNT162b2, is an mRNA vaccine—the newest type of vaccine in development.

The vaccine works by delivering snippets of genetic material that carry instructions for making the COVID-19 spike protein—the protein that the coronavirus (SARS-CoV-2) uses to infect cells.

The mRNA is packaged inside a slippery coating that allows it to slide into cells and tell them to make the spike protein. This prompts an immune response to protect you from catching COVID-19.

In animal tests, mRNA vaccines have also shown promise for treating and preventing certain types of cancer and infectious diseases, such as the flu and Zika virus. So far, no mRNA vaccines are widely available for preventing infections in people.

The Pfizer/ BioNTech vaccine isn’t the only mRNA vaccines for COVID-19 now in Phase 3 trials. Another candidate was developed by Moderna in partnership with the U.S. National Institutes of Health.

Some 30,000 participants have enrolled in Moderna’s Phase 3 trial. Moderna announced on November 16 that its coronavirus vaccine, known as mRNA-1273, is 94.5 percent effective against COVID-19.

An independent Data and Safety Monitoring Board (DSMB) conducted a review of the company’s Phase 3 human safety trials, which are being conducted in collaboration with the National Institute of Allergy and Infectious Diseases (NIAID).

Based on that review, the Massachusetts-based biotech firm announced its positive early results. The company says it plans to submit for an Emergency Use Authorization (EUA) with the U.S. Food and Drug Administration (FDA) in the coming weeks.

One key difference between Pfizer and Moderna
The Moderna and Pfizer candidates are both nRMA vaccines. One notable difference between them, however, is the temperature at which they must be stored to remain effective.

Moderna’s vaccine remains stable for 30 days at 36° to 46°F—the temperature of a standard home or medical refrigerator.

At a colder temperature of -4°F, it could remain stable for up to six months, while it may last for 12 hours at room temperature.

Pfizer’s experimental vaccine, on the other hand, must be stored in an ultra or deep freezer at about -94° F in order to remain effective. This has prompted questions about a potential barrier to its widespread distribution.

Moderna points out that most pharmaceutical distribution companies have the ability to store and ship products globally at -4°F. 

In a November 18 announcement, however, Pfizer says it has the experience, knowledge and existing cold-chain infrastructure to safely distribute the vaccine on a global scale.

The company reports it has developed specially designed, temperature-controlled thermal shippers that use dry ice to maintain the necessary ultra-low temperatures. These shipping units can be used as temporary storage of the vaccine for up to 15 days if they are refilled with dry ice. Each unit is equipped with a heat senor to track its location and temperature during shipment.

Article sources open article sources

Pfizer. “Pfizer and Biontech Conclude Phase 3 Study of COVID-19 Vaccine Candidate, Meeting All Primary Efficacy Endpoints.” Nov 18, 2020.
Pfizer. Pfizer and BionTech Announce Vaccine Candidate Against COVID-19 Achieved Success in First Interim Analysis From Phase 3 Study. Nov 9, 2020.
U.S. Centers for Disease Control and Prevention. “Measles Vaccination.” March 2019.
Wang F, Kream RM, Stefano GB. “An Evidence Based Perspective on mRNA-SARS-CoV-2 Vaccine Development.” Medical Science Monitor. 2020;26:e924700. Published 2020 May 5.
Zhang C, Maruggi G, Shan H, Li J. “Advances in mRNA Vaccines for Infectious Diseases.” Frontiers in Immunology. 2019;10:594. Published 2019 Mar 27.
ModernaTX, Inc. “Protocol mRNA-1273-P301, Amendment 3.” Aug. 20, 2020.
U.S. National Institutes of Health. “Phase 3 clinical trial of investigational vaccine for COVID-19 begins.” Jul. 27, 2020.
Pfizer. “Pfizer and BioNTech Propose Expansion of Pivotal COVID-19 Vaccine Trial.” Sept. 12, 2020.
Moderna. “Moderna’s COVID-19 Vaccine Candidate Meets its Primary Efficacy Endpoint in the First Interim Analysis of the Phase 3 COVE Study.” Nov 16, 2020.
Moderna. “Moderna Announces Longer Shelf Life for its COVID-19 Vaccine Candidate at Refrigerated Temperatures.” Nov 16, 2020.

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