With less than four months of data — the outbreak only emerged in late 2019 — questions about immunity, especially in the long term, are difficult to answer.
However, ABC health reporters had a stab at finding out. Here’s some of what they found when talking to medical experts.
Infection with COVID-19 activates your immune system, but some people will mount a better immune response than others. To make an educated guess it’s best to look at the other four coronaviruses … that cause the common cold every year.
This immunity can last for months to years, so we could expect that SARS-CoV-2 immunity would not be forever.
Some viruses, such as polio and measles, generate antibodies that can provide lifelong immunity. For others it may be just a few years, as is seen in Severe Acute Respiratory Syndrome (SARS).
“If you look at SARS, people became immune and they probably remained immune for up to a couple of years, and then it started to decline,” Professor Rawlinson from the University of New South Wales said.
“We think [COVID-19] is likely to be similar, because the virus is so similar,” the Professor said.
What – no symptoms?!
One of the many unanswered questions is what is going on with the immune response of people who have the virus, don’t show any symptoms (asymptomatic) and those who only have very mild symptoms.
Andrew Taylor-Robinson, a professor of infectious disease immunology at Central Queensland University, said people infected with COVID-19 who were asymptomatic probably had a “very robust immune response”.
He said even mild cases were likely to generate antibodies and other protective mechanisms.
But Dr Labzin from The University of Queensland said it was possible asymptomatic people built a “smart immune response” rather than a strong one, which meant they produced fewer antibodies.
“Maybe in asymptomatic people, the immune response was in there early and managed to control things, so that they didn’t develop severe symptoms,” she said.
There have been several reports of people who have tested positive for COVID-19 after apparently recovering from the disease, fuelling concern that infection doesn’t guarantee immunity, even in the short-term.
But most experts agree these cases don’t represent reinfections and are more likely to reflect the imperfect nature of testing.
One possibility is a false negative test: where the virus never actually left the person’s body, but temporarily dipped below detectable levels, incorrectly indicating a “negative” result.
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