An individual can develop immunity either after being infected with a virus or by getting vaccinated. But the immune protection isnot always the same. Immunity evoked by the vaccine and natural immunity against SARS-CoV-2 may be different with regard to the strength of the immune response and the duration for which the protection lasts.

Furthermore, everyone does not attain the same level of immunity from infection. Immune responses to the vaccines are consistent. The difference in immune response between vaccination and natural infection appears to be greater when it comes to the new variants. Two studies published in July revealed that COVID-19 vaccines were slightly less effective against the variants than they were against the older strains of the virus; however, they still yielded excellent immune response against the new variants.

Individuals who have already been infected with COVID-19 might be susceptible to the new strains, while those who were vaccinated appeared more likely to be protected. The vaccines offer a safe and reliable means to develop immunity against the old as well as the emerging strains of coronavirus, particularly the delta variant.

While immunity after infection is unpredictable, vaccination yields reliable protection.

Following COVID-19 infection, the antibody and T cell responses can protect against reinfection. Around 84-91% of individuals who developed antibodies against the original coronavirus strain seemed to be unlikely to contract the infection again for six months, even after a mild infection. People who had no symptoms also have a likelihood of developing immunity, but they may make fewer antibodies. So, for some people, natural immunity may be strong and last for long. But everyone will not develop immunity after a SARS-CoV-2 infection. Nearly 9% of infected individuals do not have detectable antibodies, and close to 7% do not seem to have T cells that can recognize the virus 30 days following infection.

For those who develop immunity, the strength and duration of the protection tends to vary. Around 5% may lose immune protection within a few months and are vulnerable to reinfection.

Individuals who had been infected by strains present early in the pandemic may be vulnerable to reinfection from the delta variant. A study has shown that 12 months after infection, 88% of people still had antibodies that could inhibit the infection of cultured cells with the original variant; however, less than 50% of the individuals had antibodies that could inhibit the delta variant.

COVID vaccines, on the other hand, produce antibody and T cell responses. These responses tend to be stronger and more consistent than immunity after an infection. A study noted that six months after receiving the first dose of Moderna COVID-19 vaccine, 100% of the study subjects had antibodies against SARS-CoV-2. Another study assessed the Pfizer and Moderna vaccines and noted that antibody levels were way higher in vaccinated individuals compared to those who had recovered from SARS-CoV-2 infection. A study from Israel suggested that the Pfizer vaccine could block 90% of infections after both doses, even those with new variants. 

A study with the original virus has shown that vaccination after infection yields 100 times more antibodies than infection alone. Additionally, 100% of the individuals vaccinated after infection had protective antibodies against the delta variant.

So, the vaccines against COVID-19 may not be perfect, but they evoke strong antibody and T cell responses, offering safer and more reliable protection vs. natural immunity.

Source: ET Healthworld