There has been very little information on the occurrence and premise for reinfection caused by Omicron variants in patients who have been vaccinated and had breakthrough infection with SARS-CoV-2 variants. But now scientists at the Indian Council of Medical Research-National Institute of Virology (ICMR-NIV) have presented four cases where patients had breakthrough infection from the Kappa or Delta variant, and several months later were reinfected with Omicron variants, after receiving two doses of vaccine.
The details have been published in a letter in the Infectious Diseases journal on August 23. According to a systematic review in the May 2021 issue of the same journal, the recurrence of SARS-CoV-2 virus infection has been reported to vary between 2.3 per cent and 21.4 per cent. In cases of reinfection, the disease severity was found to decrease or remain unchanged at 97.3 per cent. The authors called for studies to clarify the underlying preconditions for reinfection.
The situation has become even more complicated due to the appearance of the Omicron variant with increased transmissibility and immune escape potential. The variant has now evolved into 283 sub-lineages including the most predominant BA.1.1, BA.2 and BA.4 and BA.5, according to the authors Rima Sahay, Deepak Patil, Gajanan Sapkal, Anita Shete and Pragya Yadav.
They identified four Covid-19 naive persons, who had taken two doses of the Covishield vaccine, which were administered four weeks apart. It was followed by a breakthrough infection during the second wave (April 2021) and subsequent reinfection during the third wave (January 2022) in Maharashtra. The sera were obtained at first infection, pre-reinfection, after reinfection and evaluated for the neutralising antibody responses against the prototype strain (B.1), Delta (B.1.617.2) and Omicron (BA.1).
The complete genome sequence revealed the infection with Kappa and Delta variants. Two cases of breakthrough infection (Kappa variant) were asymptomatic; while two cases (one Kappa and Delta variant each) were symptomatic with patients developing fever, sore throat, productive cough, headache, myalgia, generalised weakness, loss of appetite, loss of smell and taste. These four cases got reinfected with SARS-CoV-2 BA.2 sub lineage post breakthrough infection at a mean of 275 days. Of the reinfection cases, one patient was asymptomatic; while three other patients had mild fever, cold, cough and sore throat. The pre-reinfection sera (collected after eight months of breakthrough) for antibodies, suggested waning immune response at the pre-reinfection period.
“Even with complete doses of vaccination followed by breakthrough infection, reduced immune responses were observed at pre-reinfection. This emphasises the need for the booster vaccination dose. Apparently, the known immune escape of Omicron and its sub-lineage could also be the reason for the reinfection amongst these breakthrough cases,” say the experts.
Irrespective of the immune status with vaccination or the natural infections, many breakthrough infections and re-infections have been observed across the globe. Considering this along with booster dose vaccination, the continuation of non-pharmaceutical interventions i.e. use of mask, hand hygiene and physical distancing would be the good strategy to curb the spread of infection, the scientists urged.
