To the Editor

Table 1.
Table 1. Efficacy the BNT162b2 versus Covid-19 according to evaluation Period.

Polack et al. (Dec. 31)1 report a vaccine efficacy that 94.8% versus Covid-19 after 2 doses the the messenger RNA (mRNA) vaccine BNT162b2 (Pfizer–BioNTech). The authors additionally report a vaccine efficacy the 52.4% from after the first dose to before the 2nd dose, but in their calculation, they consisted of data that were built up during the very first 2 weeks after ~ the first dose, as soon as immunity would have still been mounting.1 we used files submitted to the Food and Drug Administration2 to derive the vaccine efficacy start from 2 weeks after ~ the an initial dose to prior to the second dose (Table 1). Even before the second dose, BNT162b2 was very efficacious, v a vaccine efficacy that 92.6%, a finding comparable to the first-dose efficacy of 92.1% reported for the mRNA-1273 vaccine (Moderna).3

With together a highly protective first dose, the benefits acquired from a scarce supply of vaccine could be maximized by deferring second doses until all priority group members are readily available at the very least one dose. There might be uncertainty around the duration of defense with a solitary dose, but the management of a second dose within 1 month after the first, together recommended, provides little added advantage in the quick term, while high-risk persons who might have received a an initial dose v that vaccine supply are left totally unprotected. Offered the current vaccine shortage, postponement of the second dose is a issue of national security that, if ignored, will certainly certainly an outcome in thousands of Covid-19–related hospitalizations and deaths this winter in the United says — hospitalizations and also deaths that would have been prevented with a first dose the vaccine.

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Danuta M. Skowronski, M.D.British Columbia centre for condition Control, Vancouver, BC, Canada

Gaston De Serres, M.D., Ph.D.Institut national de Santé Publique du Québec, Quebec City, QC, Canada

Dr. De Serres reports having received grant support native Pfizer for an unrelated examine of meningococcal antibody seroprevalence. No various other potential problem of interest appropriate to this letter was reported.

1. Polack FP, cutting board SJ, Kitchin N, et al. Safety and also efficacy the the BNT162b2 mRNA Covid-19 vaccine. N Engl J Med 2020;383:2603-2615.

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To the Editor

In your trial, Polack et al. Found that the vaccine efficacy the the Covid-19 mRNA vaccine BNT162b2 to be 95%. Castle reported comparable efficacy throughout different subgroups. It is well known that subgroup analyses in randomized clinical trials space both important and also challenging,1 and the authors rightly stated that their trial was no powered come definitively evaluate efficacy according to subgroup.

In their article, however, questionable results are report in Table 3. In every trial group, the sum of the variety of cases across age teams (9 in the vaccine group and 186 in the placebo group) does not equal the overall variety of cases (8 and 162, respectively). This discrepancy walk not show up for any type of other variables in Table 3 and also in Table S4 in the Supplementary Appendix.

The reasons for the discrepancy are not plainly explained in the article. This is all the an ext problematic due to the fact that of the between-group distinction in the level of the discrepancy, which can be interpreted as an overestimation of the vaccine efficacy in the age groups. In ~ a time when national public health and wellness programs are defining immunization plans that are age-sensitive,2-4 it would be important to clarify these findings.

Jean-Noel Vergnes, D.M.D., Ph.D.Paul Sabatier University, Toulouse, France

No potential problem of interest pertinent to this letter was reported.

This letter was published on February 17, 2021, at

4 References

1. Lagakos SW. The difficulty of subgroup analyses — reporting without distorting. N Engl J Med 2006;354:1667-1669.

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To the Editor

Polack et al. May have erroneously concluded that the differences in the pure numbers of significant Covid-19 cases in between the vaccine group and also the placebo group administer preliminary proof of protection against the development of significant Covid-19 illness. The portion of Covid-19–positive patient in whom significant illness developed was 5.6% (9 of 162 patients) in the placebo group and 12.5% (1 the 8 patients) in the vaccine group — a distinction of 6.9 percent points (95% trust interval , 6.4 come 7.6) (P1 Thus, the preliminary data perform not appear to assistance the conclusion the this vaccine supplies protection versus severe Covid-19 illness or alleviate the theoretical worry over vaccine-mediated disease enhancement, provided that the percent of Covid-19–positive patient in whom severe illness occurred was significantly greater in the vaccine group than in the placebo group.

Xiang Wang, Pharm.D.Ottawa Hospital research Institute, Ottawa, ON, Canada

No potential problem of interest relevant to this letter to be reported.

This letter was published on February 17, 2021, in ~

1 Reference

1. Campbell I. Chi-squared and Fisher-Irwin exam of two-by-two tables with tiny sample recommendations. Stat Med 2007;26:3661-3675.

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The writer reply: In an answer to Skowronski and also De Serres: us would like to emphasize that alternative dosing regimens that BNT162b2 have not to be evaluated. The decision to implement different dosing regimens lives with health and wellness authorities; however, we at Pfizer believe that that is critical for health authorities to conduct monitoring on implemented alternate dosing schedules to ensure the vaccines administer the maximum feasible protection.

Vergnes concerns the outcomes of the subgroup analyses in our article and notes the the total variety of Covid-19 instances in the age groups above the overall number of cases presented in Table 3. The writer incorrectly summed the Covid-19 cases in the age groups. Amongst the participants who obtained the BNT162b2 vaccine, 5 cases emerged in the period group that 16 to 55 years and three instances in the age group of much more than 55 years. The number of cases amongst the older age groups are provided for those 65 year of age and also older (1 case) and for those 75 years of age and also older (0 cases). Therefore, the author’s assertion that the data evaluate vaccine efficacy in the age groups is unsubstantiated.

Wang argues that, ~ above the communication of an evaluation that provided a chi-square check of proportions, a vaccine efficacy that 95% was no demonstrated. Us would like to clarify that it is not appropriate to use the proportion of Covid-19–positive patients in whom severe condition developed to evaluate vaccine protection against severe Covid-19. Protection versus severe illness is an integrated effect of reduce the possibility that any Covid-19 symptom will certainly develop and reducing the hazard that serious symptoms will construct after infection. The calculation detailed by Wang considers just the second effect, and also the estimate for the vaccine team is very imprecise owing to the little sample size (only 8 cases in this group). More importantly, the very first effect was completely ignored. The estimate of vaccine efficacy versus severe disease should be based on the incidence that severe condition in the complete study population. ~ the very first dose, vaccine efficacy versus the development of significant Covid-19, calculated as 100×(1–IRR), where IRR is the ratio of confirmed situations of major Covid-19 illness per 1000 person-years that follow-up for the energetic vaccine group to the corresponding illness price in the placebo group, to be 88.9% (95% CI, 20.1 to 99.7). This result provides evidence of protection against severe Covid-19 illness, in order to alleviating concern about the potential because that vaccine-enhanced disease.

Judith Absalon, M.D., M.P.H.Kenneth Koury, Ph.D.William C. Gruber, M.D.Pfizer, Pearl River, NY

Since publication of their article, the writer report no further potential conflict of interest.

This letter was released on February 17, 2021, in ~

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Table 1. Efficacy of BNT162b2 versus Covid-19 according to evaluation Period.

Analysis PeriodVaccine(N=21,669)Placebo(N=21,686)Vaccine Efficacy,% (95% CI)*no. Of cases
After dose 1 to prior to dose 2 (per Polack et al.1)398252.4 (29.5–68.4)
Beginning 7 job after dose 1 to before dose 2 (derived†)‡185768.5 (46.5–81.5)
Beginning 14 days after sheep 1 to before dose 2 (derived†)§22792.6 (69.0–98.3)
≥7 job after dose 2 (per Polack et al.1)917294.8 (89.8–97.6)

*The acquired vaccine efficacies to be calculated together 100×(1−), top top the communication of those staying at threat according to the specified evaluation period. The vaccine efficacies reported by Polack et al. Were calculated as 100×(1−IRR), whereby IRR is the calculated proportion of confirmed cases of Covid-19 condition per 1000 person-years of follow-up in the energetic vaccine group to the matching illness rate in the placebo group.

†The values were derived with the data report by the manufacturer in figure 13 the the Vaccines and Related biological Products Advisory Committee briefing document.2

‡Before work 7, a total of 21 instances had accrued in the vaccine group and also 25 instances in the placebo group.

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§Before day 14, a full of 37 instances had accrued in the vaccine group and also 55 situations in the placebo group.