Of late, many cases of individuals being re-infected with Covid-19 have been reported, prompting health authorities to once again stress on the need to continue taking precautionary measures. As such, fresh guidelines to curb the spread of Covid-19 and its variants including Omicron have also been issued.
In light of the same, its essential to understand why reinfection after recovery — and in some cases double vaccination — is still happening, and what can be done.
What is reinfection?
According to US’ Centers for Disease Control and Prevention (CDC), reinfection is when a person gets infected once, recovers, and then gets infected again. According to experts, based on what is known from similar viruses, some reinfections are expected. Ongoing Covid-19 studies will help us understand:
*How likely is reinfection?
*How often reinfection occurs?
*How soon after the first infection can reinfection take place?
*How severe are cases of reinfection?
*Who might be at higher risk for reinfection?
*What reinfection means for a person’s immunity?
*Whether a person is able to spread Covid-19 to other people when reinfected
In an AIIMS Delhi study, two doses of indigenously developed Covid-19 vaccine Covaxin were found to be 86 per cent effective in preventing Covid-19 reinfections in Indian healthcare workers (HCWs) during the second wave that was driven by the Delta variant. The study was published in JAMA Network Open journal.
Another National Center for Biotechnology Information (NCBI) study suggested that prior infection in patients with Covid-19 was highly protective against reinfection and symptomatic disease. This protection increased over time, suggesting that viral shedding or ongoing immune response may persist beyond 90 days and may not represent true reinfection. As vaccine supply is limited, patients with known history of Covid-19 could delay early vaccination to allow for the most vulnerable to access the vaccine and slow transmission, the November 2021 study mentioned.
Experts have noted waning immunity in patients who have recovered from Covid-19. Does that make people more vulnerable to reinfections?
Dr Sulaiman Ladhani, consulting chest physician, MD Chest and Tuberculosis, Masina Hospital, Byculla, Mumbai, believes “cases testing repetitively positive are very rare”. “Even if such cases are seen, it could be in a setting where there is high exposure for people, like healthcare workers, or those with multiple co-morbidities or extremely low immunity. But this is very rare,” he said.
Dr MD Mubasheer Ali, senior consultant, Apollo Telehealth said, “Large-scale serological screening with validated tests will identify individuals who may have protective immunity to infection and a better measure of disease activity. It is highly unlikely that Covid-19 infection strikes the person twice in a short window.”
Reinfection with Covid-19 or SARS-CoV2 is said to be a matter of scientific discussion. As of now, it is not clear whether a person who has been infected once develops permanent immunity against the disease, or can get reinfected. An understanding can help decide intervention strategies required to control the spread of the disease which can aid in assessing how long people will have to depend on masks and physical distancing, as well as vaccinations and precaution doses.
According to Dr Bipin Jibhkate, consultant critical care medicine, and ICU director Wockhardt Hospitals, Mira Road, a person can “test positive twice or thrice a month as the deadly virus is still present in the body”.
“It takes around 30 days on average for the virus to disappear after one exhibits the symptoms of Covid. It can be present for a longer time when it comes to the older population or one having a severe illness. Testing positive again and again can be shocking and worrisome for the patient, but that doesn’t mean he/she is contagious and will transmit the infection to others around. They may not have an active infection at that time. Those who keep testing positive need to follow Covid-appropriate behaviour: wear a mask, maintain social distancing, and sanitise hands. Be at home, do not allow any visitors at home,” said Dr Jibhkate.
So, do antibodies not work?
It’s not that the antibodies do not work, but there is a possibility that they “may not be sufficient antibody response to the infection”, due to which the person may not develop adequate immunity and his body is prone to infection again, asserted Dr Ladhani.
According to Dr Vishal Wadhwa, head, quality assurance MD., D.N.B Microbiology, Metropolis Healthcare Ltd, SARS Cov-2 is a highly mutable virus and has gone over 33 lakh mutations by now. “Usually, a mutation leads to viral death but rarely it encodes for a survival advantage and ensures enhanced transmission/severity of infection and immune escape. Vaccines/infection create two types of the immune responses. One is humoral (antibody) and the second is cell-mediated. Immune escape happens when the mutation occurs at the S gene which codes for the spike protein. Due to this, the existing humoral antibodies are not able to counter the fresh invasion and a person suffers from an infection; cell-mediated immunity comes into play later and is not able to prevent occurrence,” explained Dr Wadhwa.
Agreed Dr Arunesh Kumar, HOD and senior consultant- pulmonology, Paras Hospital Gurgaon and explained how “one can get Covid positive multiple times because what Covid test detects is one particular Covid infection episode”. “Like other viruses, SARS COV-2 too mutate. Mutations mean they modify their genetic core, which is essentially the nucleus of the virus. When it changes the core material, it starts behaving like a new virus and that’s why our immunity doesn’t recognise them as the same Covid virus, which we had been infected with previously,” noted Dr Kumar.
In light of cases of Omicron, a highly contagious virus, what are the possibilities? “Omicron has shown at least 47 mutations affecting all the regions of its genome including spike protein. Which means there will be an immune escape phenomenon leading to reinfections and also there will be a failure to detect SARS COV-2 by few PCR kits. In addition, there will be chance that patients will fail to respond to monoclonal antibodies and existing anti-viral antibiotics (due to mutations in the non-structural protein encoding region as well),” elaborated Dr Wadhwa.
Dr Kumar stated that another possible reason could be that the virus hasn’t been “cleared from the throat”. “Even if you’re not sick or unwell, you may still be harbouring the virus in your throat which is picked up by RT-PCR test,” said Dr Kumar.
So, what can be done?
As per Dr Wadhwa, safety precautions (protective equipment, social distancing etc.) and vaccination doses, booster dose/precaution dose can help. “These boosters will have to be taken till the time virus keeps mutating and throwing variants of concern (VOC) to us,” Dr Wadhwa noted.