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Explainer: Will COVID-19 Vaccines Protect Us? Does Efficacy Equal Effectiveness?

According to experts, a vaccine’s effectiveness can be influenced by multiple factors like the rate of spread of a virus, number of people adhering to the optimum dosing schedule and timetable, the way an individual’s immune systems responds, whether the vaccine was stored at the correct temperature, among others

Explainer: Will COVID-19 Vaccines Protect Us? Does Efficacy Equal Effectiveness?

The frontrunners in the COVID-19 vaccine race have emerged with different success rates for their shots in clinical trials, but what does that mean for the global fight against the pandemic? U.S. drugmakers Pfizer-BioNtech and Moderna have each said their coronavirus vaccines have an efficacy rate of around 95 per cent and a Russian project touted 92 per cent efficacy for its Sputnik V vaccine. Britain’s AstraZeneca announced an average efficacy rate of 70 per cent, still well above the 50 per cent rate that U.S. regulators have said they want to see before approving a COVID-19 vaccine for use.

Also Read: Centre Asks States, Union Territories To Form Block Level Task Force For COVID-19 Vaccine Rollout

What Are Efficacy Numbers?

If a vaccine has an efficacy of, say, 80 per cent, it means that if 100 people who have not previously been infected by the coronavirus are given the vaccine, on average 80 of them will not get the disease that the virus causes: COVID-19. These rates relate to vaccines administered and monitored in controlled circumstances, such as clinical trials.

Does That Mean An Individual’s Protection Level Is The Same?

No. A person immunised with a vaccine that has, say, 80 per cent efficacy is very likely to be protected from getting the disease with symptoms, especially severe ones. They are also very likely to be protected from asymptomatic disease – but this, depending on the vaccine, may be less certain. Even with 95 per cent efficacy, there is no absolute guarantee of protection for any particular individual.

Also Read: Russian Direct Investment Fund, Hetero Pharma Agree To Produce Over 100 Million Doses Of Sputnik V Vaccine In India

What Does This Mean In The Real World?

There is a difference between efficacy rates obtained in clinical trials and effectiveness – the real-world protection rate of a vaccine when it is rolled out. “Efficacy says: ‘Does it work?’. Effectiveness says: ‘Can it be applied? Can you carry the efficacy to the people?’,” said Marcel Tanner, an epidemiologist and president of Switzerland’s Academies of Arts and Sciences.

In the real world, a vaccine’s effectiveness can be influenced by multiple, unpredictable factors including, for example: the rate of spread of a virus; how many, or few, people adhere to the optimum dosing schedule and timetable; how individuals’ immune systems respond; whether the vaccine was stored at the correct temperature; whether people know, or don’t know, if they’ve been exposed before.

Generally, a vaccine’s real-world effectiveness tends to be slightly lower than its efficacy.

Will These Vaccines Stop The COVID-19 Pandemic?

Experts say this is unlikely. More realistic, they say, is that we will have to live alongside the SARS-CoV-2 virus.
Evidence so far suggests that COVID-19 vaccines developed by Pfizer-BioNtech, Moderna and AstraZeneca will help stop people developing the disease. Only AstraZeneca’s data, so far, shows signs that its shot may also help prevent transmission of the virus.

“Protection against illness has a value for an individual,” said Penny Ward,” a visiting professor in pharmaceutical medicine at King’s College London. She added, however, that vaccines that do not prevent transmission will not halt the pandemic.

Until the vaccination and other measures result in the virus being close to elimination in any particular country, and worldwide, there will still be a need for distancing, masks and hand washing to reduce transmission further than will be achieved by the vaccine alone. A vaccine is no good until people are vaccinated, and even then, it will not result in a situation where all other protective measures can be immediately abandoned, said Stephen Evans, a professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine.

Also Read: AstraZeneca CEO Expects To Run New Global Trial Of COVID-19 Vaccine

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

NDTV – Dettol Banega Swasth India campaign is an extension of the five-year-old Banega Swachh India initiative helmed by Campaign Ambassador Amitabh Bachchan. It aims to spread awareness about critical health issues facing the country. In wake of the current COVID-19 pandemic, the need for WASH (WaterSanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign highlights the importance of nutrition and healthcare for women and children to prevent maternal and child mortality, fight malnutrition, stunting, wasting, anaemia and disease prevention through vaccines. Importance of programmes like Public Distribution System (PDS), Mid-day Meal Scheme, POSHAN Abhiyan and the role of Aganwadis and ASHA workers are also covered. Only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and become a Swasth or healthy India. The campaign will continue to cover issues like air pollutionwaste managementplastic banmanual scavenging and sanitation workers and menstrual hygiene

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