WHEN Aishah Abdullah (not her real name) first contracted Covid-19 last August, the experience was horrible.
The mother of two boys aged 5 and 8 was infected by the Delta variant and suffered from high fever, body aches and diarrhoea. To make matters worse, her entire family was also infected.
Her history of asthma made recovery more challenging and she lost her sense of taste and smell for two weeks.
But little did Aishah expect that she would be reinfected two more times. Her job in the healthcare sector increases her exposure to Covid-19, and despite taking precautions after having her first infection, she got reinfected.
Her second and third infections, which occurred in March and early this month, were caused by the Omicron variant.
"The second time, my symptoms were milder and I recovered faster. But the third infection was bad. I had a severe fever and body aches again," she says.
Aishah is now trying to boost her immune system as she believes her weakened state has made her susceptible to Covid-19.
Pantai Hospital Cheras internal medicine specialist Dr Liza Ahmad Fisal says reinfection is primarily due to the growing number of variants.
She explains that the virus is evolving, producing hundreds of variants. Not all of them are clinically significant, but some may cause severe symptoms and become more transmissible.
Molecular virologist Dr Vinod Balasubramaniam said Covid-19 reinfections were rare before the emergence of Omicron.
Data shows that Delta or an earlier strain will be about 90 per cent effective in preventing reinfection in vaccinated and unvaccinated people. However, everything changed when Omicron emerged.
With Omicron, prior infections provide only about 50 per cent protection against reinfection, he explains.
Covid-19 has acquired so many mutations in its spike protein that newer versions have become better at evading the body's immune system.
"This means you can catch a version of Omicron after recovering from an older, non-Omicron variant. You can even get sick with one of the newer Omicron sub-variants after recovering from a different version of it," says Vinod, who is the leader for infection and immunity research strength at the Jeffrey Cheah School of Medicine and Health Sciences at Monash University Malaysia.
THE IMPACT
Dr Liza says for some individuals, Covid-19 reinfection will result in severe deterioration of health. This is especially true for people in the high-risk group, such as the elderly, smokers and those with comorbidities.
"Those with risk factors are more likely to end up with complications, such as lung fibrosis, making them vulnerable to severe reinfections," she says.
Vinod adds that because the virus is infecting more people, the chances of being reinfected are higher.
While it's unclear if there are some people who are simply more susceptible to Covid-19 re-infection, researchers are beginning to find some clues.
"People who are older or immunocompromised may make very few or very poor-quality antibodies, leaving them vulnerable to reinfection," says Vinod.
However, the immunity induced by prior infections and vaccination has done well in protecting against severe disease, he says.
Some people may suffer worse symptoms when they are reinfected, for example, if they have a higher viral load than in the first infection, or if their immunity against Covid-19 has waned significantly.
The elderly with underlying conditions or immunocompromised individuals, even if vaccinated, may not be as protected against severe symptoms despite previous infections.
Would a reinfected person be more likely to suffer from long Covid?
Vinod believes the risk of long Covid increases if there is a high level of the virus in your system, and it is very likely that such a condition happens the first time you are infected.
In subsequent infections, your body is better prepared to fight off the coronavirus, so you may be able to keep the virus at low levels until it is completely gone. However, this remains to be seen as immunity differs from person to person.
Dr Liza says long Covid affects up to 80 per cent of infected individuals and is commonly seen in those with severe Covid-19 and those requiring hospitalisation.
But as the cause of long Covid is unknown, it's also a mystery whether reinfection may increase the risk of getting it. However, if current theories hold true, then it is reasonable to assume that repeat infections would increase the risk of long Covid, she says.
REINFECTION RISK
*Reinfection can occur as early as 3 months after contracting Covid-19.
*New variants like Omicron are radically different from older variants and protection may wane even sooner.
*Each new subvariant of Omicron has been better able to evade immunity from vaccination than its predecessor.
*While vaccinations still provide us with some form of immunity, if BA.4. and BA.5 continues to surge, second booster doses are necessary to reduce the burden in hospitals (especially with waning immunity for individuals who received their booster doses past 6 months).
*Contributing factors for reinfection include loosening of public health measures such as masking and physical distancing and poor vaccination uptake.
*Low booster uptake is another contributing factor because vaccine efficacy wanes over time.
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