A study conducted by the All India Institute Of Medical Sciences (AIIMS) in Delhi has found that none of the vaccinated people died after getting re-infected with Covid-19 during the month of April-May 2021.
The first genomic sequence study of breakthrough infections in the country during the second wave of Covid-19 in India made this clear.
In simple terms, if one contracts Covid-19 after being fully vaccinated, it is known as a breakthrough infection. “There will be a small percentage of fully vaccinated people who still get sick, are hospitalised, or die from Covid-19,” the US health agency, Centers for Disease Control and Prevention (CDC), said.
AIIMS Delhi’s first study on breakthrough infections during the April-May period confirmed that despite a very high viral load, none of the vaccinated people died due to the disease.
Out of the 63 breakthrough infections, 36 patients received two doses, while 27 received at least one dose of the Covid-19 vaccine. Ten patients received Covishield, while 53 received Covaxin, the AIIMS researchers found.
Sars-CoV-2 lineages could be assigned to a total of 36 (57.1%) samples, 19 (52.8%) in patients who completed both doses and 17 (47.2%) in patients who completed only a single dose, the study said.
The B.1.617 variant, first detected in India, was divided into three lineages – B.1.617.1, B.1.617.2 and B.1.617.3.
The B.1.617.2 variant was found to be the predominant lineage in 23 samples (63.9%). Out of them, 12 were among the people in the fully-vaccinated group and 11 were in the partially-vaccinated group.
B.1.617.1 and B.1.1.7 lineages were found in four (11.1%) and one (2.8%) sample respectively.
“While antibody levels for a subset of patients were available, they became infected nevertheless and presented to the emergency just like other patients, putting in doubt the protection offered and or clinical relevance of total IgG as a surrogate of Covid-19 immunity. The present report is unique in many aspects,” the AIIMS report said.
None of the investigated breakthrough infections was fatal. However, all the cases were presented with five to seven days of high-grade unremitting fever.
The patients had a mean age of 37 (21-92), among which 41 were male and 22 were female. None of the patients had any comorbidities that could act as a predisposing factor for breakthrough infections.
As lineage B.1.617.2 was prevalent in this group, any significant differences in lineages among fully and partially vaccinated samples were also analysed. The difference was not found to be significant in both the groups.
In addition, differences in the prevalence of lineages based on the type of vaccine were also checked. There was no significant difference observed.
Of these breakthrough infections, 10 patients — eight with double doses of vaccine and two with single dose — had total Immunoglobulin G (IgG) antibodies assessed by Chemiluminescent Immunoassay.
Out of these 10 patients, six patients had IgG antibodies a month before the infection, while four had antibodies after the disease.
Two recent studies suggested that people infected with SARS-CoV-2 or vaccinated against Covid-19 may have lifelong immunity against the disease. This, however, does not guarantee protection from re-infection but offers hope that the human body can develop antibodies that can fight Covid-19 for long.
These studies are significant as cases of re-infection have left both scientists and the public worried and wondering whether immunity against the virus is short-lived. The fear has been that repeated vaccination — annual or six-monthly vaccination — may be required to ensure consistent immunity against Covid-19.
In studies such as the one conducted by the AIIMS, scientists found that immunity against Covid-19 lasted for a year at the least. They estimated that immunity against Covid-19 could last for decades at least in some people.