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Landmark phase 3 trial of BNT162b2 COVID-19 vaccine candidate: safety and final efficacy results


Safety and final efficacy results from the pivotal phase 3 trial of BNT162b2, the mRNA-based COVID-19 vaccine candidate, were published in The New England Journal of Medicine ( NEJM ).
In the trial of 43,448 participants, who were 16 years and older, 21,720 of whom received BNT162b2 and 21,728 placebo, the two-dose regimen of 30 µg BNT162b2, which was given 21 days apart, was well-tolerated and has demonstrated vaccine efficacy of 95% against COVID-19.

In the pivotal study, vaccine efficacy similar to that observed in the overall population was generally consistent among subgroups defined by age, gender, race, ethnicity, obesity, or presence of a comorbidity.

Among 36,523 participants who had no evidence of existing or prior SARS-CoV-2 infection by the time of the immunizations, there were 170 cases of COVID-19 observed with onset at least 7 days after the second dose; 8 cases occurred in vaccine recipients, and 162 in placebo recipients, corresponding to 95.0% vaccine efficacy ( 95% credible interval [ CI, 90.3, 97.6 ] ).
Among participants with and without evidence of prior SARS CoV-2 infection, there were 9 cases of COVID-19 among vaccine recipients and 169 among placebo recipients, corresponding to 94.6% vaccine efficacy ( 95% CI [ 89.9, 97.3 ] ).

The cumulative incidence of COVID-19 cases over time among placebo and vaccine recipients began to diverge by 12 days after the first dose, and 52.4% vaccine efficacy ( 95% confidence interval: 29.5, 68.4 ) was observed between dose 1 and dose 2, indicating the early onset of a partially protective effect of immunization.
Two doses of vaccine provide the maximum protection observed.
Ten cases of severe COVID-19 were observed with onset after the first dose. Nine cases occurred among placebo recipients and one among BNT162b2 recipients.

BNT162b2 exhibited a favorable tolerability and safety profile. Based on a data cut-off date of October 9, 2020, 37,706, participants had a median of at least two months of safety data available after dose 2 and contributed to the main safety dataset.
Among these participants, 49% were female; 83% were White; 9% were Black or African American; 28% were Hispanic / Latinx; 35% were obese ( body mass index [ BMI ] greater than or equal to 30.0 kg/m2 ); and 21% had at least one underlying comorbidity.
The median age was 52 years, and 42% were older than 55 years.

The most common adverse events of BNT162b2 were transient, mild to moderate pain at the injection site, fatigue and headache, and these generally resolved within two days.
These reactions were less common and milder in older adults than younger adults.
Severe reactions ( grade 3 ) were reported in fewer than 2% of vaccine recipients after either dose except for fatigue ( 3.8% ) and headache ( 2.0% ). Fever ( 38 °C or more ) was reported in similar proportions of younger ( 16% ) and older ( 11% ) vaccine recipients.
Rates of serious adverse events were similar between vaccine and placebo groups ( 0.6% and 0.5% ).
There were no COVID-19 related deaths.

All trial participants will continue to be monitored to assess long-term protection and safety for an additional two years after their second dose.

The ongoing clinical trial of BNT162b2 has enrolled more than 44,000 participants, the vast majority of whom have received their second dose.
The trial is designed as a 1:1 vaccine candidate to placebo, randomized, observer-blinded study to obtain safety, immune response, and efficacy data needed for regulatory review.
The trial’s primary endpoints are prevention of COVID-19 in those who have not been infected by SARS-CoV-2 prior to immunization and prevention of COVID-19 regardless of whether participants have previously been infected by SARS-CoV-2. Secondary endpoints include prevention of severe COVID-19 in those groups.
The study also will explore prevention of infection by SARS-CoV-2, the virus that causes COVID-19. ( Xagena )

Source: Pfizer & BioNTech, 2020

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