Those who have managed to avoid catching COVID-19 so far into the pandemic must be wondering if it’s just luck or something else.
Could it be diligent mask-wearing or proper hand hygiene or timely vaccinations that played a role? Or could there be a chance you had COVID-19 but were just asymptomatic?
What does the data say?
It’s almost been 2.5 years since the World Health Organization first declared COVID-19 a pandemic. More than 9.5 million confirmed COVID-19 cases have been reported in Australia throughout the pandemic to date.
According to this systematic review and meta-analysis of 95 unique studies with 29,776,306 individuals undergoing testing, the pooled percentage of asymptomatic infections was 0.25% among the tested population and 40.50% among the population with confirmed COVID-19.
But even taking into account people who have had COVID-19 without realising it, there is still likely a group of people who may have never had it.
What might be some of the reasons why someone hasn’t had COVID at all?
The reason why some people appear to exhibit a stronger immunity to COVID-19 is the subject of intense investigation.
Here are some theories
And while the jury is very much still out, here are some theories for some individual’s stronger immunity:
Theory 1: Lack of certain receptors
As discussed in an article by the Conversation, one theory around why some people may have avoided COVID-19 is that even if COVID-19 enters their respiratory system, it may not have progressed to the stage of infection. This could occur, for instance, if there is a lack of the receptors available in the individual, which are needed for SARS-CoV-2 to gain access to cells. The absence of such receptors may be genetic.
Once a person does become infected, however, researchers have identified that differences in the immune response to SARS-CoV-2 may play a role in determining the severity of symptoms. It is possible that a quick and robust immune response could prevent the virus from replicating much if at all.
Theory 2: T-cell memory
There are seven coronaviruses that infect humans: four that cause the common cold, and one each that cause Sars (severe acute respiratory syndrome), Mers (Middle East respiratory syndrome) and COVID.
In an interview with ABC, infectious diseases specialist Dr Paul Griffin said that research has found that people with higher levels of memory T-cells from other coronavirus infections — such as the ones responsible for common colds — are less likely to become infected with SARS-CoV-2.
How long-lasting this immunity may be is another question.
In conclusion
Ultimately, no doubt, a combination of care and/or luck is likely to have played a part in many people avoiding COVID-19 infection to date.
On this score, Dr Griffin deserves the final word:
“It might depend on how likely a person is to attend crowded events or other high-risk venues, if people aren’t necessarily doing a lot of that, then it will reduce their risk. I think if people get complacent, having thought they’ve achieved something by now and stop doing all of those things, then there’s every chance that they will go off and get infected, probably in the not-too-distant future.”
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