As Covid-19 cases across the world observe a significant dip, most of its success can be attributed to the Covid vaccines manufactured by various companies in India and overseas which has helped in bringing down the mortality rate of this deadly disease considerably.
To date, more than 183.01 million people have been infected with the coronavirus worldwide, with over 3.96 million fatalities.
As we talk about vaccines, it is important to understand what the efficacy rate of each vaccine is which has played an important role in determining the advent of Covid-19. In a nutshell, the efficacy value indicates a relative reduction in infection risk and not an absolute probability of protection against Covid-19 despite being vaccinated.
To determine the efficacy rate of a vaccine, drugmakers run a trial among selected participants of different layers of the population divided into two groups, half get the vaccine and half a placebo. After a certain period, researchers count how many people got infected from Covid-19 in these two groups.
The vaccine efficacy determined in the trials is just a snapshot of the virus in the world at that given time. When the vaccine goes out into the general population, the prevalence of the virus might have changed and any variants that may be circulating.
Let us find out what the efficacy of these vaccines in use are;
Pfizer-BioNTech
On December 11, 2020, Pfizer became the first Covid-19 vaccine to receive an FDA EUA, after the company reported positive clinical trial data. In early May, the Pfizer-BioNTech vaccine was found to be more than 95% effective against severe disease or death from the Alpha variant (first detected in the United Kingdom) and the Beta variant (first identified in South Africa) in two studies based on real-world use of the vaccine. As far as the Delta variant (first seen in India), two studies reported by Public Health England showed that full vaccination (after two doses) is 88% effective against symptomatic disease and 96% effective against hospitalization.
Moderna
Moderna’s vaccine was the second one authorized for emergency use in the U.S. about a week after the Pfizer vaccine. Moderna is also an mRNA vaccine, using the same technology as the Pfizer-BioNTech one and with similarly high efficacy that is 94.1% at preventing symptomatic disease. However, the Moderna vaccine was slightly less effective in clinical trials about 86% in people who are 65 and older. Some research has suggested that Moderna’s vaccine may provide protection against the Alpha and Beta variants.
Johnson & Johnson
On February 27, 2021, the FDA granted emergency use approval for a different type of vaccine, called a carrier, or virus vector, vaccine. In comparison to the Pfizer and Moderna vaccines, this one is easier to store (in refrigerator temperature), and requires only a single shot, which has made it easier to distribute and administer. It is said to have 72% overall efficacy and 86% efficacy against severe disease in the U.S. According to the analyses the FDA released in late February, there was 64% overall efficacy and 82% efficacy against severe disease in South Africa, where the Beta variant was first detected.
AstraZeneca
Similar to the Johnson & Johnson vaccine, this is a carrier vaccine, made from a modified version of a harmless adenovirus. AstraZeneca updated its data analysis of its phase 3 trials in March, showing its vaccine to be 76% effective at reducing the risk of symptomatic disease 15 days or more after receiving the two doses, and 100% against severe disease. The company also said the vaccine was 85% effective in preventing COVID-19 in people over 65.
Novavax
This vaccine has been shown to be effective not only against COVID-19, but also against the mutations that have emerged in Great Britain and, to a lesser extent, South Africa. The company says the vaccine was 91% protective of people in high-risk populations such as people older than 65, those with health conditions that increase risk of complication, and those in situations where they are frequently exposed to the Novavax says the vaccine is 93% effective against “predominantly circulating variants of concern and variants of interest,” and 100% against variants “not considered variants of concern.
Covishield
The Covid-19 vaccine was developed by Oxford University in partnership with British-Swedish firm AstraZeneca. It is being manufactured in India by Pune-based Serum Institute of India (SII). Studies of the efficacy of Covishield vaccine have been wide-ranging. According to AstraZeneca, primary analysis of Phase 3 clinical trials show that the vaccine had an efficacy of 76 per cent against symptomatic Covid-19. With an inter-dose interval of 12 weeks or more, vaccine efficacy increased to 82 per cent.
Sputnik V
The Sputnik V vaccine has been developed by Gamaleya National Research Institute of Epidemiology and Microbiology in Moscow, Russia, in partnership with the Russian Direct Investment Fund (RDIF). It is being distributed in India by Dr Reddy’s Laboratories, based in Hyderabad. According to results published in The Lancet, the efficacy of Sputnik V was found to be 91.6 percent after Phase 3 trials.
Covaxin
Bharat Biotech’s Covaxin has demonstrated 77.8 percent effectiveness against symptomatic COVID-19 and 65.2 percent protection against the new Delta variant. The company on Saturday said it concluded the final analysis of Covaxin efficacy from Phase 3 trials. The efficacy analysis demonstrates Covaxin to be 93.4 percent effective against severe symptomatic COVID-19 cases while safety analysis shows adverse events reported were similar to placebo, with 12 percent of subjects experiencing commonly known side effects and less than 0.5 percent feeling serious adverse events. The efficacy data demonstrates 63.6 percent protection against asymptomatic COVID-19, a release from the city-based vaccine maker said.
Sinopharm
Amid growing concerns about protection against the Delta variant, many countries from China to Indonesia and Brazil rely heavily on Chinese vaccines to inoculate their people against COVID-19. Researchers found that Chinese vaccines are somewhat effective in reducing the risk of symptomatic and severe cases caused by Delta.
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