Recently, German Chancellor Angela Merkel gave a speech about the importance of slowing down Covid-19. Among her remarks were
The most important thing, the chancellor said, is to slow down the spread of the coronavirus to win time for people to develop immunity
How does that work? Can immunity be developed without actually catching the disease or via a vaccine?
It's hard to know exactly what another person is thinking, but Merkel is probably referencing herd immunity.
Assuming that people who are infected and recover will be less susceptible to infection in the future (the extent to which is currently unknown), those people have effectively been naturally vaccinated, which can help slow down future spread.
Merkel and other world leaders were likely talking about herd immunity (they may have walked that back now) but we don't know if the immunity from the infection is long-lasting or not. For instance, it is said seasonal coronavirus immunity lasts less than a year so they're not particularly immunogenic.
Furthermore, the virus has several mutations and we don't know if exposure to one mutation is sufficient to produce immunity against another. Given that's it's not particularly immunogenic it seems it won't.
When people are infected with OC43 and HKU1—two other coronaviruses that regularly circulate among humans and cause common colds—they stay immune for less than a year. By contrast, immunity against the first SARS virus (from 2003) holds for much longer. No one knows whether SARS-CoV-2 will hew to either of these extremes, and according to one recent study, its behavior could mean anything from annual outbreaks to a decades-long quiet spell.
Immunity can be built by a bigger group of people that has been infected and healed from the sickness. This immunity of the group gives the virus no chance to spread again.
no chance is too strict. It will be harder to spread is more appropriate.
