MASS VACCINATION WILL be needed for populations to reach herd immunity and prevent further resurgences of the pandemic, a new study based on data from Wuhan has found.
Published in The Lancet, the study suggests that 6.9% of the population of the Chinese city had Covid-19 antibodies by April 2020.
Of these, 40% of people had developed neutralising antibodies – which protect against future infection – and these remained stable for at least nine months.
Further, 82% of participants who had tested positive for Covid antbodies had not experienced any symptoms of the disease.
Wuhan was where the first cases of a “pneumonia of unknown origin” were reported in December 2019.
The study involved sourcing data from over 9,000 participants. Blood samples were taken to test if antibodies were present in mid-April 2020, mid-June and between October and December.
Of the 9,542 participants, 532 had antibodies against Covid-19. Four in five participants who had antibodies were asymptomatic cases. The study’s authors said this is much higher than other estimates reported around the world. They said this may be due to recall bias where a person is asked to report their own symptoms months later.
Due to the relatively low presence of the disease among the population, researchers said that is unlikely that herd immunity will be achieved without effective mass vaccination campaigns.
Its lead author Dr Chen Wang, from the Chinese Academy of Medical Sciences and Peking Union Medical College, said: “Assessing the proportion of the population that have been infected with SARS-CoV-2 and who are immune is of utmost importance for determining effective prevention and control strategies to reduce the likelihood of future resurgence of the pandemic.
Given that individuals with mild infections might not seek medical care and that asymptomatic individuals are not usually screened, there may be large discrepancies between the reported Covid-19 cases, and actual infected cases, which has been proven by the experiences and data from other countries.
In a linked comment on the study, Professor Richard Strugnell and Dr Nancy Wang from the Doherty Institute in Australia said: “Given the relative paucity of neutralising antibodies through natural infection, the study by He and colleagues reinforces the need for effective Covid-19 vaccines in the population-level control of the disease.
“The extraordinary, rapid, and effective control measures implemented in Wuhan might have restricted the spread of the virus, but also reduced naturally-acquired herd immunity by truncating the development of sustained neutralising antibodies.”
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