NIV researchers said the findings of the study prove the immune evasion potential of the Omicron variant, even after infection and vaccination. In the case of the 38-year-old healthcare professional from New Delhi, researchers at NIV said the patient had a breakthrough infection with Delta derivative (AY.112) and reinfection with the Omicron sub-lineage BA.2. Although the clinical specimens of the primary infection couldn’t be characterised, the probability of B.1 as an infecting variant would be higher as the infection occurred in October 2020, when emerging variants had not been detected in India.
“During these three episodes of Covid-19 infection, the man did not require hospitalisation and received treatment for symptomatic infection under home isolation,” researchers said.

According to NIV scientists, the fight against Covid-19 is far from over. Although vaccine boosters or third doses have shown an augmentation in the immune response against the Omicron variant, it has been found to wane over time. In such a situation, non-pharmacological interventions in the form of mask, hand hygiene and infection control remain the most reliable weapons to curb the direct transmission of SARS-CoV-2, researchers said.

While vaccination reportedly reduces severity of disease and mortality in Covid-19, it cannot protect individuals from getting a breakthrough infection. Worldwide cases of breakthrough infections have been reported, especially with the Delta variant. India, during the second wave of the pandemic in March-June 2021, was severely affected with the Delta variant of SARS-CoV2. Nationwide genomic surveillance of breakthrough cases showed the predominance of Delta variant in causing the infection.

The emergence of the highly-mutated Omicron variant also led to an enormous rise in Covid-19 cases. There was a surge of reinfection as the variant evaded the immune response from both vaccination and SARS-CoV2 infection.

In the current case, NIV researchers said the healthcare professional from Delhi tested positive with SARS-CoV2 on October 9, 2020. This was a primary SARS-CoV-2 infection, which occurred during the first wave of the pandemic. The symptoms included body ache, fever and a dry cough. However, there were no complaints of breathlessness and the man’s vitals were normal. Post recovery, the patient experienced symptoms of long Covid, including generalised weakness for two to three weeks and insomnia for two to three months.

According to NIV researchers, the patient received the first dose of Covishield vaccine on January 31, 2021, and the second dose on March 3.

The healthcare professional experienced body ache and headache again in November 2021. Subsequently, he tested positive for SARS-COV-2 and while the body ache persisted for two to three days, the person remained afebrile with no other symptoms. Recovery was uneventful except for some forgetfulness (‘brain fog’ linked to Covid-19).

The case represented abreakthrough infection post primary SARS-CoV-2 infection and two doses of Covishield vaccination. However, during the third wave of the pandemic, the healthcare professional developed a headache on January 24, 2022, after being asymptomatic for a period of two months.
He was in home isolation for seven days and the recovery was uneventful, except for increased forgetfulness post reinfection. During these three episodes of Covid-19 infection, the 38-year- old man did not require hospitalisation and he received treatment for symptomatic relief under home isolation.