> We're more likely to reach herd immunity before a vaccine is approved, sooner the better Herd immunity only really works if it's a disease we build a long te

> We're more likely to reach herd immunity before a vaccine is approved, sooner the better Herd immunity only really works if it's a disease we build a long term immunity to after being infected or vaccinated. So far we don't know how long we build an immunity to COVID-19. It is unknown (as of April 2020) if past infection provides effective and long-term immunity in people who recover from the disease.Some of the infected have been reported to develop protective antibodies, so acquired immunity is presumed likely, based on the behaviour of other coronaviruses. Cases in which recovery from COVID‑19 was followed by positive tests for coronavirus at a later date have been reported. However, these cases are believed to be lingering infection rather than reinfection, or false positives due to remaining RNA fragments. Some other coronaviruses circulating in people are capable of reinfection after roughly a year. https://en.wikipedia.org/wiki/Coronavirus_disease_2019#Immunity https://en.wikipedia.org/wiki/Coronavirus_disease_2019#Immun... Plus there's also the risk that COVID-19 mutates like influenza and norovirus: Herd immunity itself acts as an evolutionary pressure on certain viruses, influencing viral evolution by encouraging the production of novel strains, in this case referred to as escape mutants, that are able to "escape" from herd immunity and spread more easily. At the molecular level, viruses escape from herd immunity through antigenic drift, which is when mutations accumulate in the portion of the viral genome that encodes for the virus's surface antigen, typically a protein of the virus capsid, producing a change in the viral epitope. Alternatively, the reassortment of separate viral genome segments, or antigenic shift, which is more common when there are more strains in circulation, can also produce new serotypes. When either of these occur, memory T cells no longer recognize the virus, so people are not immune to the dominant circulating strain. For both influenza and norovirus, epidemics temporarily induce herd immunity until a new dominant strain emerges, causing successive waves of epidemics. As this evolution poses a challenge to herd immunity, broadly neutralizing antibodies and "universal" vaccines that can provide protection beyond a specific serotype are in development. https://en.wikipedia.org/wiki/Herd_immunity https://en.wikipedia.org/wiki/Herd_immunity