Immunity of COVID-19 survivors may last for some decades – but it only lasts for others and 11% never develop ANY protection against reinfection, the study indicates
- Researchers looked at blood samples from 164 patients previously infected with COVID-19 in Singapore
- About 11% never had detectable levels of neutralizing antibodies, while about 55% decreased levels within six months
- The remaining one-third had levels that did not fluctuate for at least six months, and some even rose levels after the time frame.
- Most patients have high levels of T cells, a type of white blood cell, even among the group that has never had detectable neutralizing antibodies.
The length of immunity to coronavirus after being infected can vary greatly from person to person, a new study suggests.
Researchers have found that some individuals who have neutralized antibodies to COVID-19 antibodies have seen their levels decrease after a few days or even a few weeks.
But at least one-third of the participants had no change in levels after at least six months, and some even raised the levels, suggesting that their immunity could last for decades.
At least 10 percent have never even had observable levels.
The team, from Duke-NUS Medical School in Singapore, says the findings provide evidence that some previously infected patients are more likely than others to be re-infected during subsequent waves, or even by many infectious variants.
A new study from Duke-NUS Medical School in Singapore found that 11% of COVID-19 survivors never had detectable levels of neutralizing antibodies (far left), while approximately 55% decreased levels within six months ( second from left and middle)
The remaining one-third had levels that did not fluctuate for at least six months, and some levels even rose after that time. Pictured: A patient being tested to see if he has coronavirus antibodies in Baldwin Park, California, February 2021
“The most important message from this study is that the longevity of functional neutralizing antibodies against SARS-CoV-2 can vary greatly and it is important to monitor this on an individual level,” the author, Dr. Wang Linfa, director of the Program in Emerging said. Infectious diseases at Duke-NUS Medical School.
“This work may have implications for the longevity of immunity after vaccination, which will be part of our follow-up studies.”
For the study, published in The Lancet Microbe, the team looked at 164 COVID-19 patients in Singapore for six to nine months.
The patients each gave blood samples, which the researchers analyzed for the neutralization of antibodies and for T cells, which are a type of white blood cell that binds to and kills viruses.
The data were then used to create an algorithm to predict the trajectories of neutralizing antibodies over time.
Participants were divided into five groups depending on how long their antibodies against COVID-19 lasted.
The first group, called the ‘negative’ group, never had detectable neutralizing antibodies and made up about 11.6 percent of the patients.
The next group, the ‘rapidly declining’ group, accounted for 26.6 percent of the patients and had fluctuating early levels of antibodies within a few days.
Subsequently, the group ‘slowly decreased’ antibodies that faded within six months, making up 29 percent of the participants.
The so-called ‘persistent’ group, which makes up 31.7 percent of the participants, showed little change in their antibody polls for at least six months.
Finally, the group with delayed response, 1.8 percent of the patients, showed an increase in neutralizing antibodies during the study period.
However, the study found that most patients have high levels of T cells, even among those in the ‘negative’ group.
This implies that individuals can still be protected if they have a strong T cell response, despite low levels of neutralizing antibodies.
‘Our study investigates neutralizing antibodies that are important for COVID-19 protection. We have found that antibodies against SARS-CoV-2 decrease against different people against different people, ” says the author, Dr David Lye, director of the National Center for Infectious Diseases in Singapore.
‘It emphasizes the importance of public health and social measures in the ongoing response to pandemic outbreaks.
“However, the presence of T-cell immunity offers hope for long-term protection, which requires more studies and time to confirm epidemiological and clinical evidence.”