The Omicron BA.4 and BA.5 sub-variants of SARS-CoV-2 have proven to be stealthier at evading people’s immune defences than all of their predecessors. But a new study shows that prior Omicron infections among vaccinated people offer four times greater protection against new variants of SARS-CoV-2.
The study, published in the New England Journal of Medicine journal shows that vaccinated people (the so-called hybrid immunity) who were infected by the earlier Omicron sub-variants BA.1 and BA.2 continue to confer immunity for the variants. Compared to vaccinated but not infected by these variants, infected people have four times greater protection against the new variants like BA.5, the study has found.
Infections in 2020 and 2021 that occurred through infection with earlier variants of the SARS-CoV-2 (ancestral lineage, Alpha and Delta variants) also confer protection against infection for the more recent Omicron variant. This protection, however, is not as high as that of individuals infected with the Omicron BA.1 and BA.2 variants at the beginning of 2022.
The researchers, analysing the registry of Covid-19 cases in Portugal found that prior SARS-CoV-2 infection reduced the risk for BA.5 infection.
The protection effectiveness, related to the uninfected group, for a first infection with Wuhan-Hu-1 was 52.9% (95% CI, 51.9 – 53.9%), for Alpha 54.9% (51.2 – 58.3%), for Delta 62.3% (61.4 – 63.3%), and for BA.1/BA.2 80.0% (79.7 – 80.2%).
They concluded that infection with BA.1/BA.2 reduces the risk for breakthrough infections with BA.5 in a highly vaccinated population. This finding is critical to appraise the current epidemiological situation and the development of adapted vaccines.
The worry: Excessive use of steroids to save life during the Covid Delta wave may have led to another health problem. Over the past one year, many such patients have developed AVN — avascular necrosis — a disease that results from temporary or permanent loss of blood supply to the bone and bone tissues.
“There are three conditions in Covid-19 that can lead to AVN — use of steroids, the infection itself as it leads to blood clot, and combination of both. The problem is we have no exact data on how many patients were given steroids,” said Dr Rajesh Malhotra, head of AIIMS Trauma Centre and an orthopaedic surgeon.
What’s AVN? A person faces bone collapse that leads to pain in joints and losing mobility in case of hip bones. At AIIMS alone, 150 patients have reported AVN, and 15 of them had to undergo hip replacement.
A proposal: AIIMS Delhi earlier submitted a proposal to Indian Council of Medical Research for a multicentric study to probe AVN cases. However, it is yet to be accepted.
Magnitude: Professor C S Yadav, president of National Knee & Hip Joint Replacement Foundation, said the number of AVN cases had doubled compared with the pre-pandemic era. “If earlier we saw two cases in a week, that has now gone up to four-five cases,” he said.
Problems galore: AVN starts showing its symptoms late, and hence, many patients are coming now, he noted. However, AVN is not new, it’s also caused by prolonged use of corticosteroids, an anti-inflammatory drug used for asthma and rheumatic conditions. It is also used for COPD-ICU conditions. More details here
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Written by: Rakesh Rai, Sushmita Choudhury, Jayanta Kalita, Prabhash K Dutta Research: Rajesh Sharma