Covishield, Covaxin: the findings of a large efficacy study

The overall effectiveness against severe Covid was 80 per cent with two doses of Covishield, and 69 per cent with two doses of Covaxin.

People receive vaccines for Covid-19 at a vaccination drive in Agartala. (Express Photo/File)

Results from a large study, which includes the Indian Council of Medical Research (ICMR), indicate that both Covishield and Covaxin significantly reduce the risk of severe Covid-19 and against the Delta variant among Indians aged 45 years and above. The study, pending peer review, was published on a preprint recently.

The findings

The overall effectiveness against severe Covid was 80 per cent with two doses of Covishield, and 69 per cent with two doses of Covaxin.

Vaccine effectiveness was highest with a 6-8 week interval between two doses of both vaccines. However, according to senior author Dr Manoj Murhekar, Director of ICMR–NIE (National Institute of Epidemiology), there were not enough numbers to gauge a 12-week interval. “The main point here is vaccines are effective. We do not really need a booster immediately as by June this year at least 60 per cent of the country’s population was infected with SARS-CoV2 and vaccination would have served as a boost to the immune system,” he said.

Another senior author, Dr Pragya Yadav, from ICMR-National Institute of Virology, said Covaxin and Covishield were effective against severe Covid-19 during the dominance of Delta variant in the second wave.

Main author Tarun Bhatnagar from ICMR-NIE, Chennai, said an escalation of the two-dose coverage with vaccines is critical to control the pandemic in the country.

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The study

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The study was conducted between May and July 2021 in 11 hospitals. Of 1,073 cases of severe Covid and 2,264 controls (Covid-negative individuals), 6 per cent cases and 17 per cent controls reported full vaccination, and 16 per cent cases and 28 per cent controls reported partial vaccination with Covishield. The effectiveness of full vaccination was 80 per cent.

Of 887 cases and 1,384 controls, 3.4 per cent cases and 5.3 per cent controls reported full vaccination and 16 per cent cases and 28.3 per cent controls reported partial vaccination with Covaxin. The effectiveness of full vaccination was 69 per cent.

The study was conducted along with researchers from Amrita Institute of Medical Sciences, Kochi; Hamdard Institute of Medical Sciences and Research, New Delhi; AIIMS-Jodhpur, JSS Medical College, Mysuru; Government Medical College, Nagpur; SRM Medical College, Chennai; JIPMER-Puducherry; Surat Municipal Institute of Medical Education and Research, AIIMS-New Delhi, Rishikesh, and Bhubaneswar; and ICMR-National Institute of Virology, Pune.

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Anuradha Mascarenhas

Anuradha Mascarenhas is a Senior Editor at The Indian Express, based in Pune. With a career spanning three decades, she is one of the most respected voices in Indian journalism regarding healthcare, science and environment and research developments. She also takes a keen interest in covering women's issues . Professional Background Education: A gold medalist in Communication and Journalism from Savitribai Phule Pune University and a Master’s degree in Literature. Author: She authored the biography At The Wheel Of Research, which chronicles the life and work of Dr. Soumya Swaminathan, the former Chief Scientist at the WHO. Key Focus: She combines scientific accuracy with storytelling, translating complex medical research into compelling public and human-interest narratives. Awards and Recognition Anuradha has won several awards including the Press Council of India's national award for excellence in journalism under the gender based reporting category in 2019 and the Laadli Media award (gender sensitivity -2024). A recipient of the Lokmat journalism award (gender category-2022), she was also shortlisted for the RedInk awards for excellence in journalism-2021. Her debut book At The Wheel Of Research, an exclusive biography of Dr Soumya Swaminathan the inaugural chief scientist of World Health Organisation was also nominated in the Popular Choice Category of JK Paper AUTHER awards. She has also secured competitive fellowships including the Laadli Media Fellowship (2022), the Survivors Against TB – New Research in TB Media Fellowship (2023) and is part of the prestigious 2025 India Cohort of the WomenLift Health Leadership Journey.” Recent Notable Articles (Late 2025) 1. Cancer & Specialized Medical Care "Tata Memorial finds way to kill drug-resistant cancer cells" (Nov 26, 2025): Reporting on a breakthrough for triple-negative breast cancer, one of the most aggressive forms of the disease. Discipline, diet and purpose; How a 97-year-old professor defies ageing'' (Nov 15, 2025) Report about Prof Gururaj Mutalik, the first Head of Department at Pune's B J Government Medical College who at 97 credits his longevity to healthy habits and a strong sense of purpose. 2. Environmental Health (The "Breathless Pune" Series) Long-term exposure even to 'moderate' air leads to chronic heart, lung, kidney issues" (Nov 26, 2025): Part of an investigative series highlighting that even "safe" pollution levels are damaging to vital organs. "For every 10 µg/m3 increase in PM2.5 level, there was 6-8% jump in medicine sales" (Nov 23, 2025): Using commercial data to prove the direct link between air quality and respiratory illnesses in Pune. 3. Lifestyle & Wellness News "They didn't let cancer, diabetes and heart disease stop them from travelling" (Dec 22, 2025): A collaborative piece featuring survivors who share practical tips for traveling with chronic conditions. At 17, his BP shot up to 200/120 mmHG; Lancet study flags why child and teen hypertension doubled between 2000 and 2020'' (Nov 12,2025)--A report that focusses on 17-year-old-boy's hypertensive crisis and reflects the rising global trend of high blood pressure among children and adolescents. 4. Scientific Recognition & Infrastructure For promoting sci-comm, gender diversity: IUCAA woman prof highlighted in Nature" (Nov 25, 2025): Covering the global recognition of Indian women scientists in gender studies and physics. Pune researchers find a spiral galaxy like the Milky Way from early universe'' (December 3, 2025)- A report on how Indian researchers discovered a massive galaxy that existed when the universe was just 1.5 billion years old , one of the earliest to have been observed so far. Signature Beat: Health, Science & Women in Leadership Anuradha is known for her COVID-19 reportage, where she was one of the first journalists to provide detailed insights into the Covishield and Covaxin trials. She has a dedicated interest in gender diversity in health and science, often profiling women researchers who are breaking the "leaky pipeline" in STEM fields. Her writing style is scrupulous, often featuring interviews with top-tier scientists and health experts from various institutions. ... Read More