A team of scientists from Spain has recently evaluated the efficacy of an mRNA-based coronavirus disease 2019 (COVID-19) vaccine developed by Pfizer-BioNTech (BNT162b2). Their findings reveal that a 2-dose regimen of BNT162b2 vaccine is capable of providing almost 100% protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in healthcare workers. The study is currently available on the medRxiv* preprint server.
Since declared a pandemic by the World Health Organization (WHO) on March 11, 2020, COVID-19 has infected 126 million individuals and claimed 2.7 million lives globally. At the initial phase of the pandemic, when COVID-19 specific therapeutics or vaccines were largely unavailable, several vital control measures including widespread testing, contact tracing, and isolation had been strictly implemented by the regional and national authorities of many countries to control the viral transmission. Simultaneously, explicit efforts had been made by the entire scientific community to design and develop safe and effective prophylactic vaccines against COVID-19.
Currently, a considerable number of COVID-19 vaccines with acceptable safety and efficacy levels are rolling out in many countries. The primary aim of the global COVID-19 vaccination programs is to immunize and protect healthcare and other front-line workers and vulnerable individuals.
In the current study, the scientists have explored the efficacy of Pfizer-BioNTech COVID-19 vaccine BNT162b2 in reducing the rate of new SARS-CoV-2 infection among healthcare workers. BNT162b2 is a lipid nanoparticle-formulated, mRNA-based vaccine that contains prefusion stabilized, membrane-bound full-length spike protein of SARS-CoV-2 as an immunogen. The clinical trials conducted for this vaccine have shown that a 2-dose regimen of BNT162b2 is capable of providing 95% protection against COVID-19.
A total of 2,590 healthcare workers were evaluated in the study. The rate of new SARS-CoV-2 infections was examined at three time points: one week before commencement of the vaccination; 1 – 4 weeks after the 1st dose; and one week after the 2nd dose. The prevalence of new infections among healthcare workers was compared to that of the general population in the same geographical region. During the study period, the vaccination rate in the community was less than 5%.
Of 2,590 healthcare workers, 1,820 received the 1st dose in the 1st week of vaccine launch and 296 in the next week. The 2nd vaccine dose was administered to the participants 21 days after the 1st dose. The weekly rate of new SARS-CoV-2 infection was measured among healthcare workers using antigen test or CRP test. Similarly, infection rates in the general population depicting the progress of the 3rd COVID-19 wave were obtained from the official records published by the regional and national authorities.
The study findings revealed that compared to a 7% reduction in the general population, the infection rate dropped by 63% among healthcare workers within 2 – 4 weeks after receiving the 1st vaccine dose. Furthermore, a 99% reduction in new SARS-CoV-2 incidence was observed among healthcare workers after one week of receiving the 2nd vaccine dose, as compared to a 68% reduction in the community.
The study highlights the importance of widespread vaccination programs in protecting healthcare workers from acquiring SARS-CoV-2 infection in the workplace. Moreover, the study suggests that even a single dose of the COVID-19 vaccine may be sufficient to provide substantial protection.
During the study period, the vaccination rate in the community was less than 5%. Thus, it is unlikely that the reduction in SARS-CoV-2 incidence observed in the community is due to the vaccine effect. The scientists believe that government-implemented public health measures might play an important role in reducing the infection rate in the community. However, the drastic reduction observed among the healthcare workers strongly upholds the importance of mass vaccination programs.
Regarding COVID-19 vaccine response, there is evidence suggesting that individuals previously infected with SARS-CoV-2 exhibit strong immune responses to a single vaccine dose. The scientists believe that the robust protection observed in the study might be due to the fact that 30% of the study participants were previously infected with SARS-CoV-2.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.