The highly infectious Delta variant of the novel coronavirus is triggering a surge of COVID-19 cases across the world, resulting in a fresh spate of restrictions being imposed extensively across the European Union as well as other countries. Infections have also been on the rise in the US, which has been one of the hardest hit by the pandemic, alongside Brazil and India. This has raised concerns about new waves of infections since the mutations in the variant enable it to escape the immune response generated by COVID-9 vaccines.
Even though cohesive data on the efficacy of vaccines against the Delta variant isn’t clear cut, patterns emerging from different parts of the world do offer some insight into the odds of warding off COVID-19 for those fully or partially vaccinated.
EFFECACY OF COVID-10 VACCINES IN PROTECTION AGAINST DELTA VARIANT
Last week, the World Health Organization (WHO) said that Pfizer-BioNTech and AstraZeneca vaccines worked effectively in preventing severe COVID-19 caused by the Delta variant, in comparison to other mutations of the virus. However, the efficacy of the vaccines in offering protection against symptomatic illness was less.
Besides WHO, several countries too are offering data on vaccine efficacy vis-à-vis the Delta variant based on their studies. Research done in the UK found that the Pfizer vaccine was 88% effective against the Delta variant, and this immunity kicks in two weeks after the second dose has been administered. The same study found AstraZeneca (which is also available in India as Covishield) to be 60% effective, after both doses.
A Canadian study found the Pfizer vaccine to be 87% effective after two doses and Moderna 72% with one dose. It also found that two doses of the vaccine offer the same degree of efficacy against the delta variant as they did against the Alpha, which was the predominant cause of coronavirus infections in the US.
THIS STUDY WAS RELEASED ON JULY 3, AND IS YET TO BE PEER-REVIEWED.
Likewise, a study carried out in Scotland found Pfizer to be 79% effective and AstraZeneca 60%, after two weeks of getting the second dose. It also categorised the Pfizer vaccine efficacy against the Delta variant as “very good”.
Based on a study, the health ministry of Israel, in a statement, said that Pfizer was 64% effective against the Delta variant after both doses. However, both Israeli health officials and Pfizer were quick to add that this study was based on highly localised and preliminary infection numbers.
In India too, the Indian Council of Medical Research has released findings of its study that offers broadly similar conclusions that individuals who have received two doses of COVID-19 vaccines had a better immune response to the Delta variant. This was true for both healthy individuals as well as those who had contracted the coronavirus after being vaccinated.
WHY DO THE NUMBERS VARY?
Different studies have thrown up different figures for the same set of vaccines. This naturally raises questions about why the numbers vary. To put it in perspective, let’s first understand what vaccine efficacy percentage means. If the efficacy for a vaccine is listed as 80%, this means that 80% of the people who have been vaccinated have full protection against infection and 20% don’t.
The varied figures from different studies are a reflection of the challenge of assessing vaccine efficacy in the real world. The vaccine efficacy for any infectious disease is typically assessed during trials, where scientists have complete control over the environment, right from selecting participants to monitoring who gets the vaccines and placebo, as well as the reaction to infections in those who’re given the vaccine. This generates a trove of methodical data.
However, in the real world, exercising the same level of control is impossible. There is no way of governing who gets vaccinated and who doesn’t. Besides, the incidence of infections and severity of the disease is influenced by a host of factors that can not only be not controlled but also in many instances not assessed. This makes arriving at firm conclusions trickier and more difficult.
For instance, those who chose to not get vaccinated may also be the ones who don’t believe the potentially catastrophic effects of COVID-19. The naysayers could, thus, be more prone to put themselves in risky situations by flouting safety norms such as mask-wearing and physical distancing.
The numbers can also vary depending on what’s being measured for a particular study, how and when it’s being measured, and the demographics it’s taking into account.
Be that as it may, there is still one clear take away from all of these studies: getting fully vaccinated with whatever vaccine is available to you gives you the best fighting chance against COVID-19.