Even with complete doses of vaccination followed by breakthrough Covid infection, reduced immune response was observed at pre-reinfection points, emphasising the need for booster doses, said an ICMR-NIV study. The study appeared in the Journal of Infectious Diseases published by Taylor & Francis.

Apparently, the known immune escape of Omicron and its sub-lineage, could also be the reason for the reinfection among these break-through cases, it said.

The authors have added that irrespective of the immune status, with vaccination or natural infections, many breakthrough and re-infections have been observed across the globe. Considering this along with booster dose vaccination, the continuation of non-pharmaceutical interventions — use of mask, hand hygiene and physical distancing — “would be the good strategy to curb the spread of infection”.

The research paper has carried out four case studies, where a few weeks after receiving two doses of vaccine, these patients underwent breakthrough infection with Kappa or Delta variant, and were reinfected several months later with Omicron variants.

It was found that the infection occurred at mean of 31 days (±9.5 days) post second dose of Covishield vaccination. Two cases of breakthrough infection (Kappa variant) were asymptomatic, while two cases (one Kappa and Delta variant each) were symptomatic and displayed fever, sore throat, productive cough, headache, myalgia, generalised weakness, loss of appetite and loss of smell and taste.

Subsequently, these four cases got reinfected with SARS-CoV-2 BA.2 sub-lineage, post breakthrough infection at a mean of 275 days (±7.5 days). Of the reinfection cases, one patient was asymptomatic, while three other patients had mild fever, cold, cough and sore-throat.

Recurrence of SARS-CoV-2 virus infection has been reported to vary between 2.3 per cent and 21.4 per cent, according to the article. In cases of reinfection, the disease severity was found to decrease or remain unchanged in 97.3 per cent.

The authors had called for studies to clarify the underlying pre-conditions for reinfection. After that, the situation has become even more complicated, much due to the appearance of the Omicron variant, which is more transmissible and has greater immune escape potential.

Omicron has now evolved into 283 sub-lineages, including the most predominant BA.1.1, BA.2 and BA.4 and BA.5.

“Many of these highly mutated versions of SARS-CoV-2 have led to global rise in SARS-CoV-2 cases and reinfections,” the article added, pointing out that there is little information on the occurrence and premises for reinfection caused by Omicron variants in patients “previously undergoing vaccination followed by breakthrough infection with SARS-CoV-2 variants”.

comment COMMENT NOW