Title : Interpretation of non-responders to SARS CoV 2 vaccines using WHO International Standard
Coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was declared a pandemic. Questions about non-responders to SARS-CoV-2 vaccines remain unaddressed. Here, we report data from people after administering the complete dose of SARS-CoV-2 vaccines using the World Health Organization International Standard for anti-SARS-CoV-2 immunoglobulin (Ig). Our study showed that immune cells such as CD4 cells, CD8 cells, and B cells and anti-spike IgG levels were significantly reduced in the elderly (60 years and older). There were 7.5% of non-responders in the age group of 18 to 59 years and 11.7% in the age group of 60 years and older. An individual with a titer of anti-SARS-CoV-2 spike IgG that is below 50 BAU/mL is considered a non-responder at 30 to 90 days after the last vaccine dose. Booster vaccination may be recommended for non-responders to reduce disease severity and mortality. There are several potential strategies that are suggested to quickly end the COVID-19 pandemic: (1) increase the vaccination rate of the population; (2) develop vaccines against emerging and potential variants; (3) administer booster vaccines for non-responders; (4) accelerate clinical trials of intranasal SARS-CoV-2 vaccines to prevent transmission; (5) assessment of humoral immune response in children, the elderly, and immunocompromised individuals within 1 to 3 months after administering the fourth dose; and (6) incorporate additional protective measures for individuals with persistent (fourth or fifth dose) negative humoral immune response after booster vaccination, such as injection of anti-SARS-CoV-2 immunoglobulins, antiviral drug treatment, and use of N95 masks in endemic areas.