Wonder what the full meaning of the statement that the (Pfizer/BioNTech) Covid vaccine is 95%?

In the final efficacy analysis, among participants [a] without evidence of SARS-CoV-2 infection before and during vaccination regimen [b], vaccine efficacy (VE) for the first primary efficacy endpoint against confirmed COVID-19 [c] occurring at least 7 days after Dose 2 [d] was 95.0% [e] (95% CI 89.9% to 97.3%), with 8 COVID-19 cases in the vaccine group compared to 162 COVID-19 cases in the placebo group [f].

a= Age 16 to 90 year-old, predominantly White American (USA 76% and Argentina 15%)

b= Among all participants (regardless of evidence of infection before or during the vaccination regimen), 50 cases of COVID-19 occurred after Dose 1 in the vaccine group compared with 275 cases in the placebo group, indicating an estimated VE of 82% (95% CI: 75.6%, 86.9%) against confirmed COVID-19 occurring after Dose 1, with VE of 52.4% (95% CI: 29.5%, 68.4%) between Dose 1 and Dose 2.

c= positive virological test plus at least one COVID-19 symptom as defined by WHO and CDC (see Appendix 1 in the attached document).

d= A number of confirmed cases of COVID-19 are not captured in the analyses of the first primary endpoint for the evaluable efficacy population because they occurred less than 7 days after Dose 2, or because they occurred in participants who were excluded from the evaluable efficacy population or who had evidence of infection before or during the vaccination regimen.

e= Incidence of Covid-19 in the vaccine and control group was 0.04% (8/18198) and 0.88% (162/18325), respectively. The risk of Covid-19 averted by the vaccine is 95% or 0.95 (0.88-0.04/0.88). The absolute risk difference in contracting the SARS-CoV-2 is 0.84% (0.88-0.04), the lowered risk by the vaccine, and the relative risk of contracting Covid-19 without the vaccine is 22 (0.88/0.04).

f= A follow-up of < 14 weeks after the second dose. The early onset of protection is only apparent approximately 14 days after Dose 1 (from cumulative incidence curves).

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Safety/ Adverse event

Local reactions were most frequently reported. After Dose 1 and Dose 2, among the 37,586 participants with a median of 2 months of follow-up after Dose 2 immediate AEs were low in frequency (0.4%). In the vaccine versus placebo groups with injection site pain were 0.3% vs 0.2%, and 0.2% vs 0.1%, after Dose 1 and 2, respectively.

In the vaccine group, pain at the injection site was reported more frequently in the younger group (16-55 years of age) than in the older group (>55 years of age). The frequency was similar after Dose 1 compared with Dose 2 of the vaccine in the younger group (83.1% vs 77.8%) and in the older group (71.1% vs 66.1%).

In the vaccine group, frequencies of redness and swelling were similar in the younger and older age group after Doses 1 and 2. Frequencies of redness were similar after Dose 1 compared with Dose 2 of the vaccine in the younger age group (4.5% vs 5.9%) and in the older age group (4.7% vs 7.2%). Frequencies of swelling were similar after Dose 1 compared with Dose 2

Across age groups, local reactions for the vaccine group after either dose had a median onset day between Day 1 and Day 3 (Day 1 was the day of vaccination) and ranges were similar in the younger and older age groups. Across age groups, local reactions for this group after either dose resolved with median durations between 1 to 2 days, which were similar in the younger and older age groups.

Systemic events were generally increased in frequency and severity in the younger age group (16-55 years of age) compared with the older age group (>55 years of age), with frequencies and severity increasing with the number of doses (Dose 1 vs Dose 2).

· Fatigue: younger group (47.4% vs 59.4%) compared to older group (34.1% vs 50.5%)

· Headache: younger group (41.9% vs 51.7%) compared to older group (25.2% vs 39.0%)

· Muscle pain: younger group (21.3% vs 37.3%) compared to older group (13.9% vs 28.7%)

· Chills: younger group (14.0% vs 35.1%) compared to older group (6.3% vs 22.7%)

· Joint pain: younger group (11.0% vs 21.9%) compared to older group (8.6% vs 18.9%)

· Fever: younger group (3.7% vs 15.8%) compared to older group (1.4% vs 10.9%)

Vomiting and diarrhea were exceptions, with vomiting reported similarly infrequently in both age groups and diarrhea reported at similar incidences after each dose.