Explained: Should the gap between Covid-19 vaccine doses be stretched?

Covid-19 vaccine: In the wake of global studies, several scientists have called for stretching the interval between the two doses to up to three months.

Written by Anuradha Mascarenhas

Pune | Updated: March 2, 2021 02:35 PM IST

4 min read

A vaccine for Covid-19 is administered to an elderly person, in Delhi on Monday (Express Photo: Praveen Khanna)

In India’s vaccination programme, the prescribed interval between the two doses of Covishield is 28 days. In the wake of global studies, several scientists have called for stretching the interval to up to three months.

The India regimen

Regulatory studies in the country have said the interval should be four to six weeks. These findings are based on Phase 3 studies.

Till date, India’s vaccination coverage has crossed 1.43 crore. Of 66.69 lakh healthcare workers who have received the first dose, 24.56 lakh have got the second and final jab. The second dose started on February 13 for those who had completed 28 days after the first dose.

Also in Explained | Explained: What is the Covid-19 vaccination process in India?

Global findings

The WHO’s advisory group SAGE on February 10 suggested an 8-12-week interval between doses. And on February 19, The Lancet published results of a study that showed a three-month interval between doses of the Oxford-AstraZeneca vaccine results in higher efficacy than with a six-week interval, with the first dose offering 76% protection in the three months between doses. Covishield is a version of the Oxford-AstraZeneca vaccine.

“The cumulation of evidence around the world shows there is 20% to 30% greater efficacy by stretching the interval between two doses. So why would we not want to do that,” leading vaccine scientist Dr Gagandeep Kang told The Indian Express.

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Oxford Professor Andrew Pollard, lead author of the study in The Lancet, has said: “Where there is a limited supply , policies of initially vaccinating more people with a single dose may provide greater immediate population protection than vaccinating half the number of people with two doses.”

To stretch interval…

“The government should very seriously consider this. A 20% increase in efficacy when you give it to millions of people is tens of thousands of new infections prevented . You can give more doses to more people, export vaccines to more places. Yes , Covid infections are showing a rise but we need to plan. Where there is little disease one can stretch the interval of doses,” Dr Kang said.

“There is ample evidence from the Lancet paper that one gets pretty good short-term protection from the first dose,” she said.

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Scientists at Serum Institute of India (the Covishield manufacturer) also noted that the longer the interval between doses, the better the protection observed, and it happens with all vaccines.

Dr Shashank Joshi, expert on Maharashtra’s Covid-19 task force, noted that several doubts have been raised about the interval. “A gap of four weeks is reasonable but ideally the 8-12 weeks is better. Recent data suggests that the immune response is better with a gap of 8-12 weeks as adopted by the UK government. The Indian government may also implement this strategy,” Dr Joshi said.

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… Or not to

Prof Sanjay Rai, president of Indian Public Health Association, said the vaccine is precious and there is a need for judicious use. He said clinical trials were the best evidence and had more weightage than observational studies, and felt it was better to give both doses within the time frame laid down by the Centre’s drug regulator until such time that more robust evidence can be generated.

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

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