The Pfizer and BioNTech mRNA Vaccine for COVID-19 Conferred 95% Protection With a Satisfactory Safety Profile

Chloroquine and Hydroxychloroquine maybe an alternative to fight against Covid-19 while scientists are doing research for a vaccine
Pfizer and BioNTech release safety and efficacy data from phase 2/3 trials for their COVID-19 mRNA vaccine.

The 2-dose BNT162b2 mRNA vaccine from Pfizer and BioNTech for coronavirus disease 2019 (COVID-19) conferred 95% protection over a median of 2 months, according to results published in The New England Journal of Medicine.

Adults (N=43,448) aged 16 years or older were recruited for this trial beginning July 2020 at 152 sites worldwide. Of these, 130 sites were in the United States, 9 in Turkey, 6 in Germany, 4 in South Africa, 2 in Brazil, and 1 in Argentina.

In this ongoing multinational, pivotal efficacy trial, investigators randomized participants in a 1:1 ratio to receive 30 mg doses of BNT162b2 intramuscularly 21 days apart (n=21,720) or placebo (n=21,728). The primary endpoints were efficacy of the vaccine against laboratory-confirmed COVID-19 and safety, observed until 6 months after the second dose. Adverse event data up to 14 weeks after the second dose are included in the report.

By the data cut-off date, a total of 37,706 participants had a median of 2 months safety data available. These participants were 49% women, 83% White, 28% Hispanic, 9% Black, 35% were obese (BMI ³30.0 kg/m2), and 21% had at least 1 comorbid condition.

Among patients with reactogenicity data (n=8183), data showed that vaccine recipients reported more local reactions than placebo. Mild-to-moderate injection site pain was commonly reported and less than 1% reported severe pain. Patients older than 55 years reported less pain (first dose: 71%; second dose: 66%) compared with younger patients (first dose: 83%; second dose: 78%).

After the second dose, systematic reactogenicity was more common among younger vaccine recipients (fatigue: 59%; headache 52%) than older recipients (fatigue: 51%; headache 39%). A similar pattern was observed among younger recipients (fatigue: 23%; headache 24%) and older recipients (fatigue: 17%; headache 14%) after the second placebo dose. Severe systematic reactions were reported by less than 2% of participants.

Severe adverse events was similar in the vaccine and placebo groups (0.6% and 0.5%, respectively), including lymphadenopathy (64 vs 6), injury or condition leading to study withdrawal (4 vs 0), and death (2 vs 4). Investigators concluded that the deaths were not related to the study.

After the second dose, a total of 9 vaccine and 169 placebo recipients were diagnosed with COVID-19, corresponding with a 94.6% efficacy (95% CI, 89.9%-97.3%). Between the first and second doses, 39 of the vaccine and 82 of the placebo recipients were diagnosed with COVID-19, corresponding with a 52% efficacy (95% CI, 29.5%-68.4%).

This study was limited by its sample size and inherent time constrains. This study was able to detect adverse events with an incidence of rate 0.01%, but not for more rare events. Follow-up data through 14 weeks was only available for ~50% of the participants, though the follow-up will continue for 2 years.

These results indicated the BNT162b2 mRNA vaccine for COVID-19 was highly efficacious through 2 months with little evidence of severe adverse events among adults aged 16 years and older.

Disclosure: Multiple authors declared affiliations with the pharmaceutical industry. Please refer to the original article for a full list of disclosures.


Polack FP, Thomas SJ, Kitchin N, et al; for the C4591001 Clinical Trial Group. Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. N Engl J Med. Published online December 31, 2020. doi:10.1056/NEJMoa2034577.