Vaccination efforts started in late 2020 in an attempt to contain the spread of the coronavirus disease (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
To date, more than 128 million people have been infected with SARS-CoV-2. Of these, over 2.8 million people have died and 72.54 million have recovered.
Currently, SARS-CoV-2 vaccines come in many types, including attenuated vaccines, messenger ribonucleic acid (mRNA) vaccines, DNA vaccines, and viral vector vaccines.
Now, researchers at the U.S. Centers for Disease Control and Prevention (CDC) COVID-19 Response Team revealed that two of the mRNA vaccines, the BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) COVID-19 vaccines are highly effective in preventing infection among health care workers, first responders, and other front liners in eight United States locations between December 2020 and March 2021.
The study, published in CDC's Morbidity and Mortality Weekly Report (MMWR), highlights the efficacy of mRNA vaccines in protecting against SARS-CoV-2 infection.
Effective in preventing symptomatic COVID-19
The two messenger RNA (mRNA) vaccines BNT162b2 by Pfizer-BioNTech and mRNA-1273 by Moderna effectively prevent symptomatic SARS-CoV-2 infection in randomized placebo-controlled Phase III trials.
These vaccines have also been granted Emergency Use Authorizations (EUAs) by the Food and Drug Administration and regulators across many countries.
However, these vaccines' benefits for preventing asymptomatic and symptomatic infections, especially when administered in real-world situations, are still unclear.
In the study, the team utilized prospective cohorts of health care personnel, first responders, and other essential and frontline workers in eight U.S. locations between December 14, 2020, and March 13, 2021.
The participants were part of HEROES-RECOVER, a network of longitudinal cohorts in eight U.S. locations, including Tucson, Phoenix, and other Arizona areas, Florida, Miami, Duluth, Minnesota, Portland, Oregon, Temple, Texas, and Salt Lake City, Utah. The participants enrolled in the study in July 2020.
To arrive at the study findings, 3,950 health care workers, first responders, and other frontline workers completed weekly SARS-CoV-2 testing for 13 weeks. The CDC conducted the testing regardless of symptom status and at the onset of symptoms consistent with COVID-19-associated illness.
The researchers performed surveillance for symptoms of COVID-19, such as chills, fever, cough, shortness of breath, sore throat, diarrhea, muscle pain, or loss of smell or taste. They conducted weekly text messages, e-mails, and made use of direct participants and medical records.
Further, the participants provided weekly self-collected midturbinate nasal swabs, regardless of COVID-19-associated illness symptom status. They also collected an additional nasal swab and saliva specimen at the start of COVID-19-associated illness.
Further, the participants reported their receipt of SARS-CoV-2 vaccines through self-report in electronic surveys, through direct upload of vaccine card images, telephone interviews, and electronic medical records.
Of the participants with no previous laboratory documentation of COVID-19, 62.8 percent received both recommended mRNA dosages, while 12.1 percent received only one dose of the mRNA vaccine.
Of those unvaccinated, 1.38 SARS-CoV-2 infections were validated by reverse transcription-polymerase chain reaction (RT-PCR) per 1,000 person-days. On the other hand, of the fully immunized participants, 0.04 infections per 1,000 person-days were reported. In those who were partially vaccinated, 0.19 infections per 1,000 person-days were noted.
Therefore, the team estimated the mRNA vaccine efficacy for preventing infection was 90 percent for fully-immunized workers and 80 percent for partially-immunized workers.
"Authorized mRNA COVID-19 vaccines are effective for preventing SARS-CoV-2 infection in real-world conditions. COVID-19 vaccination is recommended for all eligible persons," the researchers concluded in the study.
The study also demonstrates that current vaccination efforts result in significant preventive and protective benefits among working-age adults, particularly those working in the pandemic response's frontlines.
The researchers reinforce the CDC's recommendation of getting the full two-dose immunization with mRNA vaccines.
- Thompson, M., Burgess, J., Naleway, A., Tyner, H. et al. (2021). Interim Estimates of Vaccine Effectiveness of BNT162b2 and mRNA-1273 COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Health Care Personnel, First Responders, and Other Essential and Frontline Workers — Eight U.S. Locations, December 2020–March 2021. Morbidity and Mortality Weekly Report (MMWR). https://www.cdc.gov/mmwr/volumes/70/wr/mm7013e3.htm#contribAff