Why in News?

A Hong Kong man, who recovered from COVID-19, was infected again four-and-a-half months later in the first documented instance of human re-infection.

News in Detail

• The findings indicate the disease, which has killed more than 8,00,000 people worldwide, may continue to spread among the global population despite herd immunity.
• The patient was found to have contracted a different coronavirus strain from the one he had previously contracted and remained asymptomatic for the second infection.

Previous cases

• Instances of people discharged from hospitals and testing positive again for COVID-19 infection have been reported in mainland China. 
• However, in those cases it was not clear whether they had contracted the virus again after full recovery — as happened to the Hong Kong patient — or still had the virus in their body.
• One explanation was that the virus still existed in the lungs of patients but was not detected in samples taken from upper parts of the respiratory tract. 
• Other possible causes were low sensitivity of tests and weak immunity that could lead to persistent positive results.

Doubts on vaccine immunity

• The finding does not mean taking vaccines will be useless. 
• Immunity induced by vaccination can be different from those induced by natural infection. 
• We will need to wait for the results of the vaccine trials to see how effective vaccines are.
• World Health Organization (WHO) epidemiologist Maria Van Kerkhove said that there was no need to jump to any conclusions.

Reference:

1. https://www.thehindu.com/news/international/hong-kong-reports-first-virus-reinfection/article32432526.ece