Covid reinfection rare, 65 plus group vulnerable: study

Surviving Covid-19 protects most people against reinfection for at least six months, but elderly patients are more likely to be laid low by the virus a second time, researchers reported yesterday.

An assessment of reinfection rates in Denmark last year showed that just over half a percent of people who tested positive for Covid during the first wave from March to May did so again during the second wave, from September to December.

Among these, the researchers found that initial infection with Covid-19 was likely to bestow 80 percent protection from reinfection among under-65s, but that dropped to just 47 percent in older people.

Of the over 9,000 people aged under 65 who tested positive in the first wave, just 55 -- or 0.6 percent -- tested positive again during the second wave. This compared to 3.6 percent of individuals in this age group who tested positive during the second wave but not in the first.

Meanwhile, a University of Oxford study yesterday claimed that existing vaccines may protect against the Brazilian variant of the coronavirus.  The study highlighted how a variant first found in South Africa poses the biggest headache for vaccine makers.

The scientists used blood samples from people with antibodies generated by both Covid-19 infection and the Oxford/AstraZeneca and Pfizer/BioNTech vaccines that are being rolled out in Britain.

The data showed a nearly three-fold reduction in the level of virus neturalisation by antibodies generated by the vaccines for the P.1 Brazil variant - similar to the reduction seen with the variant first identified in Kent, Britain.

The variant first identified in South Africa triggered a much larger reduction in virus neutralisation, with a 9-fold reduction in Oxford/AstraZeneca's vaccine, and a 7.6-fold reduction for Pfizer/BioNTech.