According to a study published in the journal eBioMedicine, antibodies produced in the nose decline nine months after COVID-19 infection, while antibodies found in the blood last at least a year. During the COVID infection, antibodies in the nasal fluid, immunoglobulin A (IgA), provide first-line defense by blocking the SARS-CoV-2 virus when it first enters the respiratory tract.

In the study, the researchers tested 450 participants who were hospitalized with COVID-19 between February 2020 and March 2021. They reasoned that it was the period before the emergence of the Omicron variant and before the vaccine rollout.

The researchers from the Imperial College, London, found that the nasal antibodies were only present in individuals who were recently infected. They also found that the antibodies were short-lived against the Omicron variant compared to earlier variants.

Additionally, the findings of the study also showed that vaccination is very effective in creating and boosting antibodies in the blood; however, it had very little effect on nasal IgA levels. The researchers concluded that although current vaccines are effective at boosting blood antibodies, which can prevent serious illness and death, they do not significantly boost nasal IgA antibodies. Hence, they suggested that the next generation of vaccines must include nasal spray or inhaled vaccines that will target these antibodies more effectively. 

(Source: https://www.daijiworld.com/news/newsDisplay?newsID=1031516 )