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I had Covid, when should I get vaccine? What if I miss second dose? Answers to these & more

From questions on when to get vaccinated to how long one can wait between doses and more, ThePrint brings you the answers from noted public health microbiologist Dr Gagandeep Kang.

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Bengaluru: As the second wave of the pandemic rages on in India, a number of people, including those who have either recovered from Covid-19 or have tested positive, are now ready to be vaccinated against the disease.

So, when should a recovered person get vaccinated? What happens when a person catches Covid between two doses of vaccines? What if someone misses their second dose?

ThePrint answers this and some more frequently asked questions regarding vaccination, Covid recovery, and the body’s immune response.

When should I get vaccinated after I have tested positive?

The US’ Centres for Disease Control and Prevention (CDC) recommends that a person get vaccinated immediately after recovery, while the World Health Organization (WHO) states that a person should wait six months as natural antibodies seem to likely persist in the human body until then.

In India, most doctors recommend arbitrary gaps between recovery and vaccination, typically between one and three months.

Waiting to get vaccinated after recovery not only allows others who have remained uninfected to receive their first dose, but also improves immune response, says Dr Gagandeep Kang, immunologist at Christian Medical College, Vellore.

“Getting Covid is like at least getting a vaccine dose,” said Kang. “We recommend waiting at least four to eight weeks after recovery before taking the vaccine as you have naturally made antibodies during infection. Since you would still be responding to the infection, vaccinating at that time would be a waste of the vaccine,” she explains. “WHO’s guidance of waiting up to six months is based on evidence that infection provides reasonable protection.”

Allowing the body to build up the maximal natural immunity before getting a shot to further boost one’s immune response makes more sense, she adds.

Also read: India sees sharp decline in Covid vaccination numbers though more people are eligible

What happens if I take the vaccine when I’m positive?

When we get infected, the first antibody a person’s body makes is the IgM antibody.  Production of these antibodies start a week into the infection, peaks at three weeks, and declines very quickly afterward.

About three weeks after infection, the IgG antibodies start to get produced. These are the more crucial antibodies to look out for for long term protection with most infections and vaccines, and they climb in quantity from four to eight weeks after infection. Subsequently, they decline slowly.

​The blocking of viral infection requires neutralising antibodies, and the bulk of neutralising antibodies are IgG. They are made in response to the first infection or vaccination, but for some vaccines such as the mRNA vaccines, there is little neutralisation after the first dose but the second dose provides a large rise in this antibody response.

“We do not currently have any evidence to say whether it is better or worse to get vaccinated when infected, whether in terms of immune response or any safety issue,” says Dr Kang.

However, vaccinating after recovery acts like a booster shot, with previously infected people making a very strong response with the first dose of vaccine.

What if I catch Covid in between two vaccine doses?

For a majority of people, the disease is likely to be mild or moderate, depending on how many days after vaccination exposure occurred.

If exposure and disease occurs within one to three weeks of receiving the first dose, the vaccine is unlikely to have a major effect and is not expected to modify the course of the infection. However, if a person tests positive after three weeks from their first dose, they are highly likely to only get a mild disease.

Once infected, the body starts producing antibodies, and it is once again effectively akin to getting a vaccine.

In principle, follow the same protocol, says Kang. “Wait at least four weeks after recovery before you take the second dose.”

What happens if I delay the second dose? Will I need to repeat the first dose?

Trials have indicated there are differences in timings for second doses to achieve a high level of antibodies in the system.

For the AstraZeneca-Oxford vaccine Covishield, it is 12 weeks, although the Indian recommendation is for 6-8 weeks, while for the indigenous Covaxin, a gap of four weeks is recommended, since no other interval has been tested.

But missing the second dose is no cause for worry, assures Kang. It simply postpones the boosting of the antibodies and does not result in any loss of protection in the short term. Missing the time period allocated does not require a repetition of the first dose.

“If you get your first dose and don’t get your second dose for a couple of years, you probably need to repeat your first dose,” says Kang. “If it’s a matter of weeks, you definitely don’t have to worry. Even if it’s a matter of months, you most likely don’t have to.”

Also read: Only 1.97% Indians fully vaccinated so far, UP worst performer despite largest stock

Can pregnant/lactating women take the vaccine?

Based on data, it appears safe for pregnant and lactating women to take the currently available vaccines, says Kang.

Although there have been no results from trials for Covid vaccines except for no safety signal from a small number of women who later found out that they were pregnant, large numbers of pregnant healthcare workers globally have taken the vaccine already after the vaccines were rolled out and have not had any adverse outcomes.

Antibodies induced by the vaccine (or infection) can also pass on to the foetus through the placenta. Only IgG antibodies pass through, and the most transfer occurs in the second trimester and early third trimester. Maternal antibodies in children protect for about four to six months, after which their own immune system’s efficiency improves rapidly.

Antibodies also pass through breast milk to an infant, but these are IgA antibodies that protect the gut and the upper respiratory tract.

Can I take the vaccine if I have allergies? Are there any conditions that require not taking the vaccine?

The only people who should not take the vaccine are those who have already taken the vaccine and had a severe allergic reaction to it, says Kang.

There is no evidence right now that identifies any kind of allergy to a food or a drug and associates it with the vaccine. The vaccine is safe for people with all kinds of food allergies, as well as drug allergies, including allergies to antibiotics such as penicillin.

Immunocompromised patients and those undergoing chemotherapy should take the vaccines without safety concerns. However, as they are immunosuppressed, they might not make as good an immune response as others.

Do antibody tests work after vaccination?

IgM and IgG antibodies are binding antibodies which physically bind their Y-shaped structure to the proteins on the virus, flagging it and causing macrophage cells to destroy it. They can also attract natural killer cells to come and destroy cells that are infected with the virus. They simply act as markers and may not interfere with the infectivity of the virus.

A subset of antibodies called neutralising antibodies can affect the ability of the virus to infect host cells by preventing the virus from undergoing structural changes required to gain entry.

At the moment, we do not know which antibody plays a role of protection against the virus but it is likely to be neutralising antibodies, think experts.

However, we do not know that for sure and we also don’t know what level of protection they provide, explains Kang. To identify what antibodies protect, we would need to study breakthrough infections (those who got infected after vaccination) and identify an absence of these antibodies in them..

Antibody tests on the market today measure IgM and IgG antibodies, which are also always produced when the immune response is triggered — whether after natural infection or after vaccination. We do not have a standardised neutralising antibody test that tests the response after vaccination.

“So the available antibody tests after vaccination don’t look at the right thing,” Kang says. “Commercial tests are only binding antibody tests. They tell you [if] you have been infected or vaccinated, but they don’t tell you whether you are protected or not.”

How long after the Covid shots should I take other vaccines?

Our immune systems are quite capable of handling multiple infections and don’t easily reach a point of exhaustion with just one infection, says Kang.

“The objective is to maximise immune response,” she adds. “The general guidance is that if two vaccines are to be given — live vaccines in particular — they should be given together or separated by four weeks.”

(Edited by Manasa Mohan)

Also read: Delhi hospital study finds just 16% vaccinated individuals got Covid, experts say nothing serious


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