Covid-19 vaccine----use

IN DEMAND: A medical worker shows a vial of Sinopharm’s Covid-19 vaccine in Belgrade, Serbia, last January. —Photo: AP

Let me start with a question. When you hear “this Covid-19 vaccine is 95 per cent effective”, what do you think it means?

I’ve asked this of many persons—university academics, professionals, teachers, tradesmen, labourers, schooled, unschooled, politicians—and, invariably, I get the same answer—that if you vaccinate 100 persons, 95 would be “protected” from the virus. Wrong!

Given these reportedly “high efficacy rates” (anywhere from 62 to 95 per cent), you would think the manufacturers would be proud to make the data available showing how they arrived at these numbers. But, no, it took a lot of digging to unearth the data. And I wondered why. That was the first sign things may not be as straightforward as we’ve been led to believe.

I’ll use the data from the Moderna trial to illustrate, since the figures are nice and round. There were 30,000 participants divided into two groups of 15,000 each. One group (call it MV) got the Moderna vaccine, the other (MP) a placebo. In the vaccinated group, five people “developed Covid-19 symptoms” and in the placebo (unvaccinated) group, 90 developed symptoms.

Note the very weak definition of a “case”. Anyone with flu-like symptoms is counted as “positive”. No tests were done to determine if, in fact, a person had contracted Covid-19.

Now here’s the kicker. Based on such flimsy data, such minuscule numbers, they concluded the Moderna vaccine is “94.44 per cent effective”. Say what?

Denoting the five cases in MV by v, and the 90 cases in MP by p, “vaccine efficacy” is calculated by (1-v/p) x 100. In this example, we get 100×(1-5/90) = 94.44. By such mathematical sleight-of-hand, we are advised that the Moderna vaccine is 94.44 per cent effective. Unbelievable, but true.

Based on our intuitive, but wrong, notion of “efficacy”, if we vaccinate 15,000 and the vaccine has an efficacy rate of 94.44 per cent, we would expect that 14,166 would be “protected”. Sorry, it’s just 85 (90-5).

And, even so, we are allowing that those with “symptoms” had Covid-19 (which is a far stretch). Most likely, the real number is much smaller than the puny 85.

The data for the Pfizer trial were similar. There were roughly 43,500 persons in the trial, with eight “cases” in the vaccinated group and 162 in the placebo group. The calculation for “vaccine efficacy” gives this: 100×(1-8/162) = 95.06.

The marketing for Pfizer should accurately state, “To protect 154 persons, we had to vaccinate 21,750.” Not so impressive, is it? Nobody would take Pfizer’s vaccine based on that.

But you’ll be the first in line for the shot if you hear “95.06 per cent efficacy”. Sadly, it means the same thing. And, of course, no one knows which 154 of the 21,750 persons would be protected.

So what about the new vaccine kid on the block, Sinopharm from China? Their results were published in the Journal of the American Medical Association “after more than 200 million doses had been administered worldwide”.

There were 40,411 participants, divided into three roughly equal groups—one group got the vaccine from the Beijing subsidiary, another the vaccine from the Wuhan subsidiary, and the third a placebo. Drum roll for results.

A total of 142(!) symptomatic cases (in a trial population of 40,411) were recorded—21 from the Beijing vaccine group, 26 from the Wuhan vaccine group, and 95 from the placebo group.

This gives us an “efficacy rate” of 77.89 for the Beijing group, and 72.63 for the Wuhan group.

Translated, this means you have to vaccinate over 40,000 persons to “protect” 143. Impressed?

So when authorities tell us they are following “the science”, I do hope it’s better science than this.

Interestingly, “the trial participants were mostly healthy 18-to-59-year-olds”. Now, why study persons in this age group if you plan to give the vaccine to older persons?

Was it to guarantee there were not too many “adverse events” in the trial? And is this the group (60+) we are targeting to receive the Sinopharm vaccine?

If yes, based on what study in this age group? Just asking.

Have we noticed the disparity between the trial group (18-59) and the targeted group (60+)?

So what does “95 per cent vaccine efficacy” really mean? I trust by now you have enough information to answer.

Noel Kalicharan

via e-mail


Emancipation Day, August 1, celebrates the formal end of slavery in the British Caribbean in 1834 and the final termination of the quasi-slavery “Apprenticeship” in 1838. 

During the Parade of Nations at the Tokyo 2020 Olympic Games Opening Ceremony, a special group of extraordinary athletes crossed the stage.

Bernard Linley has authored a book entitled Trinidad and Tobago Athletics History, which would be relevant at any time, but is especially so now because the country is participating in the Olympics, which began on July 20 in Tokyo, Japan.

I would like to thank the personnel at the Diego Martin Health Centre for the exemplary service they are providing in their roll-out of the Covid-19 vaccine to the public.

LeRoy Clarke was a giant among Trinidadians, a Full Man.

I knew him well, and we had a deep—and perhaps what many might think unlikely—bond.