Skip to main content

Pfizer Vaccine Efficacy Against Variants

Pfizer Vaccine Efficacy Against the B.1.1.7 and B.1.351 Variants
    According to the Centers for Disease Control and Prevention, or CDC, as of May 17, 2021, 274 million COVID-19 vaccine doses have been administered in the United States. Of these 274 million doses, 147 million doses are the Pfizer-BioNTech COVID-19 vaccine. The Pfizer vaccine has been the most popular vaccine choice among U.S. citizens and is the only COVID-19 vaccine available for those aged under 18. With the fast-spreading B.1.1.7 and B.1351 variants now dominating COVID-19 cases in the U.S., many vaccine recipients are wondering how effective, if at all, the Pfizer vaccine is against these variants. A correspondence article published in the New England Journal of Medicine on May 5, 2021, addresses the effectiveness of the vaccine against the aforementioned virus strains using data from a study conducted in Qatar.

About the Variants

    The B.1.1.7 variant originated in the United Kingdom and is found to be more transmissible, or have a faster spread than other coronavirus variants. According to the CDC COVID Data Tracker, the B.1.1.7 variant makes up 74% of all coronavirus cases in the U.S. as of May 8, 2021. This variant is now the source of most COVID-19 infections in the United States. The B.1.351 variant, which originated in South Africa, has also been deemed to be more transmissible than pre-existing strains. This variant makes up 0.7% of all coronavirus infections in the United States. (For more information on coronavirus strains see here) These characteristics have caused concern among the scientific community as an increased transmissibility will contribute to the faster spread of the coronavirus. However, if COVID-19 vaccines are still highly effective against B.1.1.7 and B.1.351, these variants will contribute much less to the rapid spread of the coronavirus. 

About the Study

    The study utilized COVID-19 data from Qatar's mass immunization campaign with the Pfizer vaccine which began on December 21, 2020. This vaccination campaign occurred during the rapid expansion of the B.1.1.7 variant starting in mid-January and the B.1.351 variant starting in mid-February across Qatar. By March 31, 2021, 385,833 individuals received at least one dose of the Pfizer vaccine and 265,410 individuals were fully vaccinated with two doses. From February 23 to March 18, 2021, 50% of the COVID-19 cases in Qatar were caused by the B.1.351 variant and 44.5% were caused by the B.1.1.7 variant. Almost all cases after March 7, 2021 were caused by either B.1.1.7 or B.1.351. 

Study Results

    At least two weeks after the second Pfizer dose, the estimated vaccine effectiveness against the B.1.1.7 variant was 89.5%. Also two weeks after the second dose, the Pfizer vaccine was found to be 75% effective against the B.1.351 variant. The overall effectiveness of the Pfizer vaccine against severe or fatal COVID-19 infection in Qatar, including the predominant B.1.1.7 and B.1.351 variants, was a high rate of 97.4%. 

    Overall, the Pfizer vaccine showed high effectiveness against COVID-19 infection and disease in Qatar, even when the prevalence of the B.1.1.7 and B.1.351 variants were high. However, the vaccine seemed to be more effective against the B.1.1.7 variant than the B.1.351 variant; the effectiveness of the vaccine against the B.1.351 variant was 20 percentage points lower than overall efficacy. Despite reduced protection against B.1.351 infection, the Pfizer vaccine still has robust protection, 90% efficacy, against severe COVID-19 infection resulting in hospitalization or death.

Implications

    This study highlights the importance of getting vaccinated now more than ever. With the B.1.1.7 variant dominating most COVID-19 infections in the U.S. and the B.1.351 variant also spreading rapidly, it is crucial to get vaccinated not only to combat the high transmissibility of these variants but to also keep yourself and others protected.

Sources

1. Abu-Raddad, Laith J., et al. “Effectiveness of the BNT162b2 Covid-19 Vaccine against the B.1.1.7 and B.1.351 Variants.” New England Journal of Medicine, 2021, doi:10.1056/nejmc2104974.

2. “CDC COVID Data Tracker.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, covid.cdc.gov/covid-data-tracker/#vaccinations.

    

Comments

Post a Comment

Popular posts from this blog

Efficacy of Masks

Do Wearing Masks Really Prevent Coronavirus            For weeks, U.S. health authorities discouraged healthy Americans from wearing masks, believing they would do more harm than good. However, other countries such as China and South Korea have required all citizens to wear a mask when entering a public setting to prevent the spread of the coronavirus. But really how effective are these masks against the coronavirus? On April 3rd, Nature Medicine published an article describing their findings based off an experiment testing the efficacy of surgical face masks against coronavirus, influenza virus and rhinovirus.   Study Findings      Their results demonstrated that surgical masks were largely effective in reducing coronavirus transmission through respiratory droplets as well as aerosol particles. Three out of ten people who did not wear a mask were infected with the coronavirus through droplet particles. Out of eleven people w...
1 comment
Read more

Breakthrough Infections

 COVID-19 Breakthrough Infections     As of August 2021, a little over 50% of the U.S. population has been fully vaccinated against COVID-19. However, despite the increasing number of vaccinated individuals and high efficacy of the vaccines, rare breakthrough cases have occurred. With the reports of breakthrough cases, or instances when people who are fully vaccinated get infected with COVID-19, many questions have arisen. How common are breakthrough infections? What are the symptoms? How severe are the cases? These questions are addressed in a peer-reviewed study investigating breakthrough cases among healthcare workers in Israel. The study was recently published in the New England Journal of Medicine on July 28, 2021.  About the Study     The study setting took place in the Sheba Medical Center, which is the largest medical center in Israel staffed with 12,586 healthcare workers. By April 28, 2021, 11,453 workers (91%) had been fully vaccinated with the ...
Post a Comment
Read more

Plasma for COVID-19 treatment

FDA Authorizes Plasma for COVID-19 Treatment                     COVID-19, which has been spreading across the globe since March, has affected the lives of Americans for over six months. Many people, including the President, are eager to eliminate the virus after a dreadful 6 months of rising cases and quarantine. To their dismay, hopes of eliminating the virus by Easter and then by August, seemed to turn into an unreachable dream for Americans. With cases rising and no sure vaccine or treatment for the virus, a future without COVID-19 seemed further and further away. Yet, this Sunday on August 23, 2020, the U.S. Food and Drug Administration authorized the first treatment for COVID-19: convalescent plasma. While the plasma has only been authorized for emergency use, many people see this authorization as progress towards eliminating the virus. However, others believe that the plasma is not as effective, and that the FDA was pres...
Post a Comment
Read more