People affected by Covid sometimes argue that they do not need vaccines because their infection gave them natural immunity against the virus. But a new study suggests that around 5th of individuals who recover from Covid may not have enough protection against future infections.
According to health experts, the best way a person can protect themselves and others from Covid, even if the person has been affected previously, is to have two doses of vaccine and the booster when offered. A recent study found that 19% of people with a once confirmed infection did not produce antibodies. These antibodies target a protein called a nucleocapsid. It is located inside SARS-CoV-2.
Only a natural SARS-CoV-2 infection can generate anti-N antibodies. The production of antibodies is provoked by vaccines against its spike protein, which resides outside the virus. 8193 adults were reported in the study who had a previous SARS-CoV-2 infection confirmed through a PCR test using the ZOE COVID smartphone app. In the subsequent two weeks, each participant also reported at least one symptom. They also responded to an invitation to undergo home anti-N antibody testing.
Between April and August 2021, the scientists behind the app sent out invites. No information is provided about when the participants logged their positive PCR results. Overall, 19% of participants tested negative for anti-N antibodies, and 81% tested positive. Participants who tested negative were primarily smokers and had one or more medical problems.
Those who tested positive tended to have had more symptoms or at least one of the classic Covid symptoms. There was no evidence of a decline in anti-N antibodies among the participants who tested positive for up to 9 months after infection. The research indicates that not everyone who has had Covid sustain their antibody response to the virus. This suggests that people should get vaccinated even if they had Covid.
According to many experts, antibodies are not essential for recovery from Covid. People with a weak immune system who have difficulty in making antibodies may experience mild Covid. People with lower anti-spike antibody levels are at higher risks of reinfection.
Shortcomings of the study –
- The results are rather simplistic and incomplete.
- According to experts, the study did not measure the responses of participants’ T cells. T-cells play an essential role in the body’s adaptive immune system alongside B cells.
- T cell responses can offer immune protection even in the absence of an antibody response or symptomatic infection.
- The study did not measure a class of antibodies IgA within mucous membranes, which are the 1st line of defense against infection in the respiratory tract.
- People vary widely in the timing of their antibody responses to infection with SARS-CoV-2 from 0–33 days from the onset of symptoms. The findings of the ZOE study might have been affected by the timing of the sample.
- The study only tested a single sample over at least nine months from symptom onset from each participant.
- For the presence of antibodies against other proteins in the virus the study did not test.
- Testing only for anti-N antibodies was a significant limitation.