Stressing the need for vaccination, doctors say that past natural COVID infection will not protect everyone against re-infection. Vaccination in fact could give higher rate of protection, they say.
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“We can’t say with certainty that past, natural COVID infection offers 100 % protection against re-infections,” said Sarita Sharma, consultant Pediatrics at PSRI Hospital in New Delhi. Pointing out that the pandemic situation is evolving, Dr. Sharma stressed that not everybody who has been infected will have protection.
‘Hybrid immunity’
Natural infection is believed to be approximately as effective as vaccination, but the protection from natural infection can be further enhanced by vaccination, through ‘hybrid immunity’ , explained Dr. Rajeev Jayadevan, vice-chairman, Research Cell of the Indian Medical Association (IMA), Kerala.
He said recurrent infections within the same community is the theme of the SARS-CoV-2 virus, adding that reinfections were mild or asymptomatic, and did not cause death or serious disease in this cohort.
“Multiple studies from India have shown rates from 8.2% (KIMS Trivandrum), 9.6% (Vellore) 16% (Calicut) and 25.3% (MAX hospitals) of breakthrough infections within a few months of vaccine roll out. These were mild or asymptomatic,” Dr Jayadevan said.
“This data will help us redirect our strategies. ‘Herd immunity’ is a myth for this virus. We need to understand that clearly, so that we don’t continue to make wrong policy decisions based on that,” he added.
Memory of virus
Explaining the basis for durable protective immunity after COVID-19 infection or vaccination, Dr. Hari Kishan Gonuguntla, consultant Interventional Pulmonologist at Yashoda Hospitals in Hyderabad said that following COVID-19 infection, the immune system retains a memory of the virus.
If a person gets exposed to the SARS COV-2 virus again, the immune cells recognise the viral pathogen and kill the pathogen. This is called immunological memory. Most studies have shown that durable memory can last more than 12 months.
“However, this will not protect everyone from re-infection. People can still have re-infection with SARS CoV-2 virus. However, the severity of illness and rates of hospitalisation is less in people with prior infection,” said Dr. Gonuguntla.
“Emergence of new strains poses a substantial risk of re-infection, which may go undetected in PCR tests. Hence vaccinating these populations who had the previous infection is a strategy to enhance immune response and develop strong resistance against the new emerging strains which are of concern,” he said.
Echoing the caution, Dr. Vijay Dutta of Indian Spinal Injuries Center said there are several reasons why past COVID infection does not protect against reinfection including the constant variations in strains.
“The virus keeps on changing and mutating. This makes it very difficult to protect us from COVID-reinfection. In such a scenario, vaccines are the only way out,” Dr Dutta said.
“Most people who get infected with the COVID-19 virus, whether or not they have symptoms, produce antibodies (proteins that fight infections) and fighter cells. On recovery, the chances of reinfection appear to be very low in the first three months. And it’s possible that even after that, the low levels of antibodies may be able to protect against reinfection. But it’s important to get fully vaccinated against COVID-19, (post the mandatory gap between the recovery and vaccination),” said Dr Suranjit Chatterjee, Senior Consultant, Internal Medicine at Indraprastha Apollo Hospitals in Delhi.
“The vaccination will further add to the immune response and protect against reinfection and the possible severe manifestation that can be caused due to it,” he added.
