Hybrid immunity offers best cover: study

Hybrid of natural infection with one dose of vaccine superior to vaccine, natural immunity

Updated - August 31, 2021 10:00 am IST

Published - August 30, 2021 11:22 pm IST - Thiruvananthapuram

Photo used for representation only.

Photo used for representation only.

A combination of natural immunity to COVID-19 (from a previous infection) and vaccine-induced immunity or hybrid immunity offers the best protection against COVID-19, a cohort study done in patients with autoimmune rheumatic diseases (AIRD) in Kochi has reported.

In fact, persons who were previously infected with COVID-19 and had a single dose of vaccine afterwards had 30 times higher antibody levels in their blood than those who had received two doses of vaccine but had not had a natural infection, says Padmanabha Shenoy, Kochi-based clinical immunologist and rheumatologist.

Dr. Shenoy and his team has been following up a cohort of 1,500 patients with autoimmune rheumatic diseases who have had COVID 19 or were vaccinated to assess their immune response. He derived his conclusions on hybrid immunity after studying the anti-spike antibody levels and neutralising antibody titres in the blood samples of 120 patients from this cohort.

The pre-print, “Hybrid immunity versus vaccine-induced immunity against SARS-CoV-2 in Patients with Autoimmune Rheumatic Diseases”, appears in Social Science Research Network, a repository for pre-prints.

Single-dose COVID-19 vaccine in healthy individuals with past COVID-19 infection seems to provide better immunity than double doses in individuals not exposed to COVID-19. The study aimed to see if the same is true for patients with AIRD who are on immunosuppressants. Four groups of 30 patients each, similar in age, sex and disease, were studied. One group had taken a single dose of Covishield vaccine after being infected previously; the second group had past infection with COVID-19 but no vaccine; the third group had no previous infection but one dose of vaccine; and the fourth group had no previous infection but two vaccine doses. In the viral neutralisation assay, those with hybrid immunity (immunity from previous infection plus one vaccine dose) could neutralise the virus better than those who received two doses of vaccine or had prior infection.


Hybrid immunity was superior to the immunity developed following natural infection. It was also found that even a single dose of vaccine produces a high level of immunity for a previously COVID-infected person. “This study has implications for national vaccination policies. As a single dose of vaccine produces a high level of immunity in previously COVID-infected patients, two doses may not be necessary. This may save close to 3 crore vaccine doses,” Dr. Shenoy said.

This high level of hybrid immunity (hybrid of natural infection with one dose of vaccine) is anticipated to last in the person’s body for a longer time, providing long lasting immunity, he added.

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