Durable antibody responses 9 months after exposure irrespective of symptoms: broader vaccine coverage still needed to reach herd immunity
By April 2020, approximately 7% of the general population in Wuhan, China had antibodies to COVID-19, mostly linked to asymptomatic infection (80%), and 40% developed neutralising antibodies that persisted for at least nine months. 
These results, reported in the Lancet, are encouraging but still show that universal vaccination is essential, irrespective of previous infection, in order to reach herd immunity.
This first study on long-term immune responses included more than 9000 residents who were tested at the end of the first lock down in April 2020, with follow up at 3, 6 and 8 months.
An accompanying editorial noted that the high percentage of asymptomatic infections is likely to account for underestimates of incidence at the time and that the study is an important milestone in understanding immunity, providing a much deeper understanding of natural seroconversion. It also describes the public health response as remarkable at a time when testing, tracing, and treatment resources were much less developed. 
- He Z et al. Seroprevalence and humoral immune durability of anti-SARS-CoV-2 antibodies in Wuhan, China: a longitudinal, population-level, cross-sectional study. Lancet. 2021; 397: 1075-1084. DOI:10.1016/S0140-6736(21)00238-5. (20 March 2021).
- Strugnell R et al. Sustained neutralising antibodies in the Wuhan population suggest durable protection against SARS-CoV-2. The Lancet, editorial comment. 397(10279);1037-1039. DOI: 10.1016/S0140-6736(21)00434-7. (20 March 2021).
This report was first published on 17 May 2020.