How long can you wait to take 2nd Covishield dose? What experts say & the science behind it

With an expert panel recommending waiting up to 16 weeks to take second the Covishield dose against Covid-19, ThePrint looks at what studies and other experts say about this.

A healthcare worker holds up a vial of Covishield vaccine | Representational image: ANI

New Delhi: An expert panel on immunisation has recommended an extension of the dosage interval of the Covishield vaccine to 12-16 weeks from 4-8 weeks.

The National Technical Advisory Group on Immunisation (NTAGI) also suggested that pregnant women be given the option to choose their vaccine while lactating women be made eligible for the shot after delivery.

However, there is no evidence of an improved response of the second dose within the 12-16 week interval.

The NTAGI has now sent these recommendations to the Modi government’s apex panel on vaccines, the National Expert Group on Vaccine Administration (NEGVA), for approval before they get implemented.

Spain became the first country in Europe to approve administering the second dose of the AstraZeneca shot in a gap of up to 16 weeks. it had diverged from the European Medicines Agency’s (EMA) authorisation to grant the approval on 30 April.

ThePrint explains the science behind increasing the dosage interval between two shots of Covishield, why it is critical for pregnant women to take the vaccination, and why breastfeeding women should get the shot.

When should I take my 2nd dose of Covishield?

The government panel’s recommendation is to wait 12-16 weeks after the first dose.

According to World Health Organization (WHO)’s chief scientist, Dr Soumya Swaminathan, there is some data for some vaccines, including Covishield that’s been developed by AstraZeneca-Oxford University, where delaying the second dose up to 12 weeks actually gives a better immune boost.

Earlier guidelines stated that the second dose of Covishield was to be taken 4-6 weeks after the first. This interval was subsequently extended to 4-8 weeks. Then, in April, the Centre advised that the second Covishield dose be taken 6-8 weeks after the first.

According to a study published in the medical journal The Lancet, the longer the gap, the higher the efficacy of this vaccine.

“Supporting a longer-interval immunisation strategy, vaccine efficacy was significantly higher at 81.3% after two standard doses given at an interval of 12 weeks or longer, compared with 55.1% when given less than 6 weeks apart,” said the study.

It also said that the antibodies were “more than two-fold higher” in people who took the second dose after a 12-week interval in comparison to those with who took it at an interval shorter than six weeks.

“These findings were supported by immunogenicity studies done in participants who were younger than 55 years, showing anti-SARS-CoV-2 spike IgG antibody responses more than two-fold higher in those who had a dosing interval of at least 12 weeks than in those who had an interval of fewer than 6 weeks,” The Lancet study said.

Speaking to ThePrint, Dr S.P. Kalantri, professor of medicine at the Mahatma Gandhi Institute of Medical Sciences, said, “The Lancet study shows that a three-month dose interval might be an effective strategy for reducing disease. It would protect the largest number of individuals in the population as early as possible when vaccine supplies are scarce.”

Dr Kalantri, who is also the medical superintendent at Kasturba Hospital, added that the longer interval between the two doses also improves protection after the second dose.

Pregnant, lactating women can be vaccinated

The NTAGI has also suggested that pregnant women could be given the choice to take any Covid-19 vaccine whereas lactating women can be given the shot any time after delivery.

Currently, both categories are not allowed to get vaccinated against Covid-19.

In April, the Federation of Obstetric and Gynaecological Societies of India (FOGSI), which has over 37,000 doctors as its members, said Covid-19 vaccines should be given to pregnant women and lactating mothers. “The very real benefits of vaccinating pregnant and lactating women seem to far outweigh any theoretical and remote risks of vaccination,” FOGSI said in a statement.

Also, according to the WHO “while pregnancy puts women at higher risk of severe COVID-19, very little data is available to assess vaccine safety in pregnancy”.

It said: “…Pregnant women may receive the vaccine if the benefit of vaccinating a pregnant woman outweighs the potential vaccine risks.”

For this reason, it said pregnant women at high risk of exposure to SARS-CoV-2 (e.g. health workers) or who have comorbidities, which add to their risk of severe disease, may be vaccinated in consultation with their health care provider.

Is getting vaccinated during pregnancy important?

America’s apex medical body, the Centers for Disease Control and Prevention (CDC), says “pregnant people are more likely to get severely ill with COVID-19 compared with non-pregnant people”.

Additionally, it said, pregnant women with Covid-19 are at an increased risk of preterm birth and might be at an increased risk of other adverse pregnancy outcomes compared with pregnant women without Covid-19.

“If you are pregnant, you can receive a COVID-19 vaccine. Getting a COVID-19 vaccine during pregnancy can protect you from a severe illness from COVID-19,” it advises.

However, the CDC also added that clinical trials that study the safety of Covid-19 vaccines and how well they work in pregnant people are “underway or planned”.

Additionally, vaccine manufacturers are also collecting and reviewing data from people in the completed clinical trials who received vaccines and became pregnant.

Should breastfeeding women go for the shot?

Based on how Covid-19 vaccines work inside the body, according to the CDC, they are “thought not to be a risk to lactating people or their breastfeeding babies”.

“Therefore, lactating people can receive a COVID-19 vaccine,” it said.

However, the CDC added that the recent reports have shown that breastfeeding people who have received Covid-19 mRNA vaccines have antibodies in their breastmilk, which could help protect their babies. It highlighted that more data is still being collected to conclude the safety. This conclusion was based on studies on Pfizer and Moderna’s vaccine candidates

But in India, mRNA-based vaccines manufactured by Pfizer and Moderna are not yet available.

In the United Kingdom, the Royal College of Obstetricians and Gynaecologists promotes the advice of the Joint Committee on Vaccination and Immunisation (JCVI) published on 30 December 2020 that there is no known risk in giving available Covid vaccines to breastfeeding women.

“Although there is a lack of safety data for these specific vaccinations in breastfeeding, there is no plausible mechanism by which any vaccine ingredient could pass to your baby through breast milk,” it had said. The JCVI is an independent expert body that advises the UK’s health departments on matters related to immunisation.

(Edited by Manasa Mohan)