Protective Immunity Against SARS-CoV-2 Short-Lived as Seasonal Coronavirus Can Reinfect People Every Year

In order to understand the length of immunity to re-infection so as to prepare for future waves of SARS-CoV-2 infection, researchers examined four strains of human seasonal coronavirus - HCoV-NL63, HCoV-229E, HCoV-OC43 and HCoV-HKU1 - that cause respiratory tract infections. The team led by Dr. Lia van der Hoek, of Amsterdam University Medical Center (Amsterdam, The Netherlands) attempted to find out how often seasonal coronavirus infections occur by examining 513 serum samples of 10 healthy adult males that were collected at regular intervals since the 1980s. The researchers measured the increases in antibodies to the nucleocapsid protein - an abundant coronavirus protein - for each seasonal coronavirus with an increase in antibodies being considered as a new infection.

The team found three to 17 coronavirus infections per patient, with re-infection times between six and 105 months. The researchers found frequent re-infections at 12 months after the initial infection. Additionally, blood samples collected in the Netherlands during the months of June, July, August and September showed the lowest rate of infections for all four seasonal coronaviruses, indicating higher frequency of infections during winter in temperate countries. The researchers believe that SARS-CoV-2 could follow a similar pattern after the pandemic.

Another study has suggested that the novel coronavirus will become a seasonal virus in countries with temperate climates once herd immunity is attained, although COVID-19 will continue to spread across the seasons until then. The study authors have noted that similar to SARS-CoV-2, other respiratory viruses also follow seasonal patterns, particularly in temperate regions. However, COVID-19 has a higher rate of transmission than other respiratory viruses such as the flu, and hence, unlike the flu and other respiratory viruses, the factors governing seasonality of viruses will be unable to halt the spread of COVID-19 in the summer months. Nevertheless, the transmission rate of COVID-19 should decline significantly once herd immunity is achieved through natural infections and vaccinations, making the SARS-CoV-2 virus more susceptible to seasonal factors.

“COVID-19 is here to stay and it will continue to cause outbreaks year-round until herd immunity is achieved,” warned study senior author Hassan Zaraket from the American University of Beirut (Beirut, Lebanon). “Therefore, the public will need to learn to live with it, and continue practicing the best prevention measures, including wearing of masks, physical distancing, hand hygiene, and avoidance of gatherings.”

Related Links:
Amsterdam University Medical Center
The American University of Beirut