key: cord-0905725-adebtr0g
authors: Pasi, A.R.
title: Comparison of CFR among vaccinated, partially vaccinated and unvaccinated study participants of VIN-WIN study
date: 2021-12-10
journal: Med J Armed Forces India
DOI: 10.1016/j.mjafi.2021.10.009
sha: 1f3f8978db109fb23c64c7b765ba6604c89a1a5d
doc_id: 905725
cord_uid: adebtr0g

nan

Case Fatality Rate (CFR) is defined as "the proportion of cases of a specified condition that are fatal within a specified time". 2, 3 The CFR calculated per total cases seems to remain the best tool to express the fatality of the disease, although it might underestimate this figure in the initial phase of an outbreak. 3 During the study period (Jan 16e May 30, 2021), a total of 10061, 1159, and 2512 cases of COVID-19 were detected among unvaccinated, partially vaccinated, and fully vaccinated study participants, respectively. Total deaths observed among unvaccinated, partially vaccinated, and fully vaccinated study participants were 37, 16, and 7, respectively.

CFR among unvaccinated, partially vaccinated, and fully vaccinated study participants was 0.37 percent, 1.38 percent, and 0.28 percent, respectively. CFR among unvaccinated is more than the CFR in Fully vaccinated, but the difference is statistically insignificant (p ¼ 0.49). CFR among partially vaccinated is four times more than the CFR in unvaccinated, and the difference is statistically highly significant (p ¼ 0.0001) ( Table 1) .

It is logical and expected that the possible reasons for high CFR in partially vaccinated study participants should have been delineated, and the role of the vaccine in reducing the COVID-19 related deaths could have been ascertained. A.R. Pasi Airport Health Officer, Airport Health Organisation, Andheri (East), Mumbai, India E-mail address: pasi.ar@gov.in CFR is expressed as a proportion where the numerator comprises of cases with fatal outcomes from among the total number of cases from a specified condition/cause, which forms the denominator. 2 Hence, all cases are required to be followed up till finality is reached (cured or fatal). However, the data which was available to us was the number of cases and deaths within each group. As this was aggregate data and not individual data points, therefore calculating CFR from this would have been inappropriate. Thus the article has not provided CFR. An appropriate denominator in this situation in which individual data is not available is in terms of "Person days". The VIN-WIN study has therefore calculated proportions of cases and deaths with person days as denominator in the 3 groups.

A ratio which could have been calculated with the available data is the daily death to case ratio. The mean daily death to case ratio in the three groups was UV ¼ 0.0550%; PV ¼ 1.277% and FV ¼ 0.693%. The difference in mean daily death to case ratio between none of the pairs of groups was statistically significant. (T-test, UV v/s PV, p-value ¼ 0.097, UV v/s FV, p-value ¼ 0.785, PV v/s FV, p value ¼ 0.361).

This implies that a fall of number in cases and deaths in PV and FV groups remained proportionate. r e f e r e n c e s

COVISHIELD (AZD1222) VaccINe effectiveness among healthcare and frontline Workers of INdian Armed Forces; Interim results of VIN-WIN cohort study

Estimating case fatality rates of COVID-19

Air Cmde AFMS (P&T), O/o DGAFMS