Medical journal did not say Covid-19 vaccines offer limited protection
Social media posts claim research by medical journal The Lancet shows that Covid-19 vaccines offer little to no protection. But the posts misrepresent one measure of vaccine efficacy referred to in an article as evidence that the inoculations are ineffective, and its authors say the shots work.
“Peer-reviewed research from @TheLancet shows that the experimental vaccines reduce your chance of catching COVID-19 by: Pfizer: 0.8% Johnson & J: 1.2% Moderna: 1.2% AstraZeneca: 1.3% So, basically no prevention,” says a May 24, 2021 Instagram post that refers to an article published on The Lancet’s website titled “COVID-19 vaccine efficacy and effectiveness—the elephant (not) in the room.”
In the United States, more than 296 million Covid-19 shots have been administered. Although the rate of new infections is declining, misinformation about vaccines continues to spread, threatening vaccine uptake.
The article is not peer-reviewed research as the posts claim, but rather analyzes other studies.
It discusses the different ways vaccine effectiveness can be assessed and says relative risk reduction (RRR) -- the most publicized figure -- should not be the only statistic used when making public health decisions. The article says that absolute risk reduction (ARR) needs to be taken into consideration to get the full picture of how effective a vaccine is.
Figures used in the social media posts are for ARR, which shows a vaccine's effects on reducing risk in an entire population, while RRR indicates individual risk compared to an unvaccinated control group.
“It is extremely disappointing to see how information can be twisted and how divisive discussions have become especially on Covid-19 vaccines, as they obviously overlap with general vaccine hesitancy and antivax segments of the population,” Dr Piero Olliaro, an author of the article, told AFP.
“We do not say vaccines do not work. We say vaccine(s) do work, and add considerations about intrinsic vaccine efficacy and their effectiveness when used in different populations,” he said.
“It is incorrect to compare vaccine(s) based on clinical trials conducted in different conditions, using relative risk reduction (RRR), and assume vaccines with lower RRR do not work well enough,” according to Olliaro, who said that studies should also report ARR.
The analysis said the Pfizer-BioNtech shot has a 95 percent relative risk reduction compared with 67 percent for AstraZeneca’s vaccine, which is not being used in the United States.
However, it found that the AstraZeneca vaccine could actually be the more effective option when ARR is considered.
When the data is examined in this way -- which takes into account the number of people needed to be vaccinated to prevent an additional case of Covid-19 -- it indicates that even the vaccines with lower RRRs can be more effective across groups with various risk factors.
The article in no way is arguing that the vaccines are not effective. It is merely pointing out that comparing the effectiveness of one vaccine versus another is not as cut-and-dried as the RRR would seem to indicate.
“Bottom line: these vaccines are good public health interventions,” Olliaro concluded.
Dr Els Torreele, another author of The Lancet article, agreed.
“Most importantly: the Covid-19 vaccines work very well!” she wrote in a Twitter thread that criticized “anti-vaxxers” for using the article “to claim all sorts of things that are wrong.”
The social media posts highlight the seemingly small ARR percentages mentioned in the article, presenting them as evidence that the vaccines are not effective.
But Dr Luis Correia, evidence-based medicine associate professor at the Bahiana School of Medicine and Public Health in Brazil, said the ARR number is usually small because people only actively experience the protection if they would have otherwise contracted the disease.
“Most will not get Covid anyway, so they would not use the protection,” but everyone should be vaccinated “in order for the minority” to be shielded from infection, Correia said.
According to a report published by the US Centers for Disease Control and Prevention, vaccines have been found to work well against the coronavirus.
“FDA-authorized Covid-19 vaccines are safe and effective,” the report says, referring to the Food and Drug Administration.