Antibodies are complex chemicals made by cells everyone has called B lymphocytes. Antibodies are always circulating in your blood, and also are present on the surface of your nose and throat. The job of antibodies is to protect you from infection with invading bacteria and viruses – viruses like the new coronavirus that is causing the COVID-19 pandemic.
There are thousands of viruses – maybe more. Once you have been exposed to a particular virus like COVID-19 and you make antibodies to it, you are almost always immune to that virus again – at least until your antibody levels fall. Most of the time antibodies against a particular virus – sometimes also called ‘antibody titers’ do slowly fall naturally. Even when the levels fall- for some viruses you still are immune for a very long time or for the rest of your life – for others…not so much.
It is not clear exactly yet how long immunity to COVID-19 will last after an exposure to the virus. However, these encouraging facts are known.
There have been two other outbreaks this century with viruses very like COVID-19: SARS in 2002-2004 – and MERS in 2015. These coronaviruses actually are more deadly even than COVID-19. The difference is – they aren’t very contagious. So, these outbreaks stayed local – to Asia for SARS, and the Middle East for MERS – and didn’t turn into a pandemic.
SARS in particular has almost the exact same structure as COVID-19. And folks who get SARS are immune to it for at least two years – maybe longer. Many, many scientists are working non-stop to figure out exactly which kind of antibodies – and how much of them – you need to be immune to COVID-19, and also how long that immunity will last.