Waning antibody responses in COVID-19: what can we learn from the analysis of other coronaviruses?

OBJECTIVES: The coronavirus disease 2019 (COVID-19), caused by the novel betacoronavirus severe acute respiratory syndrome 2 (SARS-CoV-2), was declared a pandemic in March 2020. Due to the continuing surge in incidence and mortality globally, determining whether protective, long-term immunity develops after initial infection or vaccination has become critical. METHODS/RESULTS: In this narrative review, we evaluate the latest understanding of antibody-mediated immunity to SARS-CoV-2 and to other coronaviruses (SARS-CoV, Middle East respiratory syndrome coronavirus and the four endemic human coronaviruses) in order to predict the consequences of antibody waning on long-term immunity against SARS-CoV-2. We summarise their antibody dynamics, including the potential effects of cross-reactivity and antibody waning on vaccination and other public health strategies. At present, based on our comparison with other coronaviruses we estimate that natural antibody-mediated protection for SARS-CoV-2 is likely to last for 1-2 years and therefore, if vaccine-induced antibodies follow a similar course, booster doses may be required. However, other factors such as memory B- and T-cells and new viral strains will also affect the duration of both natural and vaccine-mediated immunity. CONCLUSION: Overall, antibody titres required for protection are yet to be established and inaccuracies of serological methods may be affecting this. We expect that with standardisation of serological testing and studies with longer follow-up, the implications of antibody waning will become clearer.

Identification of hepatitis delta superinfection when investigating transaminitis in HIV/hepatitis B virus co-infection.

Hepatitis delta virus (HDV) is a highly pathogenic virus which can cause rapidly progressive liver disease in individuals with chronic hepatitis B virus and for which treatment options are limited. The incidence of sexually transmitted HDV infection is unknown. Here we report the case of a HDV seronegative man with pre-existent HIV/hepatitis B virus, taking effective tenofovir-containing antiretroviral therapy, who experienced a significant acute transaminitis with HDV antibody seroconversion and viraemia and no other identifiable cause.