40% who defeated corona still susceptible to new infection: AMC survey

AHMEDABAD: A survey by the Ahmedabad Municipal Corporation (AMC) has revealed that almost 40% of the cases who had defeated Covid-19 in the past have lost antibodies and are now susceptible to new infections.
Medical health officer Bhavin Solanki said that the city has still not reached the level of herd immunity.
“People are still susceptible to get new infection and so we cannot rely upon this low level of immunity and we have to rely on the proven preventive measures till the invention of vaccine and till it is being made available to large number of people. Wearing of masks and social distancing are absolutely necessary.
He along with Dr Jay Shah Associate professor of AMC MET and Amit Parikh head of the department Medicine in SVP said that the increase in positivity of 5.63% after 1.5 months of earlier study and that too in unlock period is very less. This confirms that the effective control by AMC over spread of Covid infection through various measures like aggressive testing, proactive identification of cases and their treatment, effective containment etc. has paid rich dividend.
Solanki said that a population based sero-surveillance study was carried out in the city during the second half of June 2020 in 30,000 people which showed an average positivity of 17.61%. A repeat sero-survey after about 1.5 months carried out from August 15 to August 29 keeping a target of 10000 samples. Revealed that With 2396 positive from the 10310 serum samples for antibodies against SARS-CoV2, the seroposltlvity against Covid19 is 23.24%. As compared to our earlier study the seropositivity also increased from 17.61% to 23.24% with an average increase of about 5.63% in population seropositivity. The seropositivity among female (25.37%) is found higher as compared to males (21.81%).
The seropositivity among those people who have contracted Covid earlier is only 60.08% (With 1091 Cases showing seropositivity from 1816 total confirmed cases). This means around 40% of such people have shown absence of antibodies despite having been infected in recent past.
The seropositivity among contacts of confirmed positive cases is 31.92%. (With 1268 Contacts of confirmed positive cases showing seropositivitIy from 3973 total contacts of confirmed positive cases). This shows that 69% of such confirmed contact cases have shown absence of antibodies.
The zone wise seropositivity ranges from 11.74% to 33.14%. It was found to be highest in North Zone (33.14%) followed by Central Zone (31.64%), East Zone (23.96%), South Zone (23.91%), West Zone (20.84%), South West Zone (18.93%) and North West Zone (11.74%).