Context: A recent study in Pune has revealed that nearly 85% of the people who had been found infected with COVID-19 in a serosurvey, had developed neutralizing antibodies. That is these people had developed immunity against the disease.


  • It looks for the presence of antibodies in people. Its purpose is to find out whether a person has been infected with the virus or not, and through random testing of people, estimate the extent of spread of the disease, or prevalence, in a population group. 
  • Detection of disease-specific antibodies confirms that the person had been infected with the virus in the past.
  • But a further test needs to be carried out to detect the presence of neutralising antibodies. 

About the recent study in Pune: 

  • So far, the study in Pune is the only study that has looked for neutralizing antibodies.
  • The study shows that while a majority of infected people do develop immunity, a significant proportion (15% in this case) do not become immune even after getting infected. 
  • Therefore, it would mean that they are at risk of reinfection
  • Therefore people who have recovered from the disease are also urged to continue to take protective measures such as practice physical distancing and wearing a mask.


  • Antibodies and immunity: 
    • Many times it is thought that everyone who is infected with a disease-causing virus, and recovers, becomes immune to the disease because they build antibodies against it. 
    • However, this is not true in all cases. 
  • Guarantee of immunity: 
    • While the creation of antibodies is necessary for the recovery process, it does not guarantee immunity against a future attack from the same virus. 
    • The immunity comes from what are known as “neutralizing” or “protective” antibodies.

Neutralizing antibodies

  • These are like other antibodies that are created to fight the disease, and are nothing but proteins. 
  • The neutralizing antibodies are a small subset of the disease-specific antibodies that are generated once an infection has occurred. 
  • Their role:
    • They become special because they have the ability to thwart the entry of the same virus inside human bodies in the future. 
    • The other antibodies help in fighting off the virus once the infection has already happened.
  • Decline with time
    • The neutralising antibodies, as also other antibodies, decrease with time. 
    • The rate of decline varies in different diseases and individuals. 
    • So, in the same time that people with low neutralising antibodies see their immunity becoming ineffective, those with higher levels could still have enough to continue to fend off the virus.

Is immunity permanent?

  • Immunity can be against some infections, but in the case of the COVID-19, it is not yet known whether the immunity acquired through natural infection lasts for how long. 
  • Factors dependent: 
    • The longevity of the immunity against a disease depends on a variety of factors, including the quantity of neutralising antibodies generated by a patient.
    • However, those with a high quantity of neutralising antibodies (or specific protein molecules) could be expected to remain immune to the disease for a longer time.

Conclusion from recent study

  • The findings of the latest study could be applied well in the small population groups within the prabhags where the serosurvey was conducted. 
  • The findings also do suggest that the disease prevalence within these population groups had reached such levels that the concept of herd immunity could be playing out.