While we don’t know much about what determines a person’s protective immunity to covid-19, Rasmussen said, a lack of antibodies after a few months does not necessarily mean that a person is vulnerable to reinfection.
Given what we already know about other kinds of coronaviruses that infect people regularly, though, it would be weird if at least some survivors weren’t susceptible to getting covid-19 again at some point. But with these other coronaviruses, studies have suggested that immunity starts to noticeably wane closer to a year or more after the first infection. The possibility of covid-19 being worse the second time is less likely, since reinfection with any germ in general tends to be milder. There is a stacking effect with some diseases, most notoriously dengue fever, and immunocompromised people are likely more at risk of having a second infection that’s just as bad or worse as the first, but both examples are exceptions to the rule.
Another crucial point is that reinfection doesn’t close the door on an effective vaccine. Some vaccines are capable of evoking a better, longer-lasting immune response than the natural infection does, and this is an express goal for the scientists developing covid-19 vaccines. Booster shots are also routinely used to refresh our immunity. Even the least effective vaccines we have, the flu shot in particular, provide a real benefit in reducing the severity and deadliness of their target illness. That said, scientists will be watching closely to figure out how our immune systems respond to any vaccine candidates.