Evaluation of neutralizing antibodies post vaccination by surrogate viral neutralization test (svnt) and its change in titer with time- a six months study

In the last two years of the COVID-19 pandemic our health care system went through major changes. A large scale screening and immunization of the community was done to overcome such pandemic situation. Virus neutralization antibodies play a crucial role in assessment of long term immunity, herd immunity, vaccine efficacy. A prospective cross sectional study was done in completely vaccinated individuals for six months in three phases. Neutralizing antibody response in individuals immunized with full two doses of vaccination were monitored by using surrogate virus neutralization test (sVNT). We found that in the second phase neutralizing antibodies has decreased with respect to the first phase. In the third phase of study (after six months of complete vaccination) the titers of the antibody fell considerably among majority of subjects. In our study the antibody titer of Covaxin was considerably more prevalent than Covishield. In our study the level of neutralizing antibodies titer fell down 3-5 months post vaccination. 42% (21) of 50 subjects were resulted negative for neutralizing antibodies during third phase of study i.e. after 6-7 months of the second dose.