tripleme
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Q: What is the rationale behind the nine-month expiry date of one's fully vaccinated status? Will my protection against Covid-19 wane by then? Will we need multiple booster shots in the future?
A: Associate Professor Hsu Li Yang, vice-dean of global health and programme leader of infectious diseases at the Saw Swee Hock School of Public Health, said a number of studies in several countries, including Singapore, show that one's neutralising antibodies start falling after two to three months in most vaccinated people. This means that protection against infection would taper off after a few months.
"Protection against severe disease, hospitalisation and death has thankfully lasted longer, no doubt because of T-cells and the adaptive immune system," he added.
The adaptive immune response refers to the second layer of immune defence in the body, which takes days or weeks to develop.
"We currently do not know how long protection against severe Covid-19 disease and death will endure, although that appears to gradually wane over time as well, especially for the elderly and immunosuppressed," noted Prof Hsu.
Agreeing, Professor Ooi Eng Eong, from the Duke-NUS Medical School's emerging infectious diseases programme, said the rate in immunity wanes is different with different vaccines and in different groups of people, and noted that the benefit for booster vaccination is "less clear at this stage" for the general population and among young adults.
"If the goal is to prevent any infection, then it is likely that we will require multiple booster shots to sustain the high levels of antibodies needed to block infection. If the goal is to prevent all symptomatic infection, including those that are mild, then annual or even six-monthly vaccination may be needed as again, the baseline level of immune activity against Sars-CoV-2 will need to be high.
"If, however, the goal is to reduce the risk of severe COVID-19 that needs hospitalised management, then there is little indication that vaccine-induced immunity has waned to those levels in healthy young adults," said Prof Ooi.
Professor Dale Fisher, a senior consultant from the National University Hospital's infectious diseases division, noted that looking at T-cells and antibodies are "laboratory approaches" to understanding immunity.
"How much does that translate to reality? For this, we need clinical data such as infections, whether mild or severe, for different age groups and whether the patient has an infection after being vaccinated, and how long it has been since they were vaccinated," he added.
The vulnerable, such as seniors, are at higher risk, which is why a booster is recommended at five to six months after the primary vaccination series.
"We know at this time we see more mild infections, and there is no appetite to wait longer to see if severe infections emerge," he added.
Early studies from Britain also suggested that a booster jab will provide 80-85 per cent protection against Omicron, compared with 97 per cent against Delta. Though current vaccines are not a perfect match against Omicron, getting vaccinated does make it harder for Omicron to infect the body.
More antibodies are developed thanks to the booster, giving the body stronger defences against the virus.
https://www.straitstimes.com/singap...when-your-fully-vaccinated-status-will-expire
A: Associate Professor Hsu Li Yang, vice-dean of global health and programme leader of infectious diseases at the Saw Swee Hock School of Public Health, said a number of studies in several countries, including Singapore, show that one's neutralising antibodies start falling after two to three months in most vaccinated people. This means that protection against infection would taper off after a few months.
"Protection against severe disease, hospitalisation and death has thankfully lasted longer, no doubt because of T-cells and the adaptive immune system," he added.
The adaptive immune response refers to the second layer of immune defence in the body, which takes days or weeks to develop.
"We currently do not know how long protection against severe Covid-19 disease and death will endure, although that appears to gradually wane over time as well, especially for the elderly and immunosuppressed," noted Prof Hsu.
Agreeing, Professor Ooi Eng Eong, from the Duke-NUS Medical School's emerging infectious diseases programme, said the rate in immunity wanes is different with different vaccines and in different groups of people, and noted that the benefit for booster vaccination is "less clear at this stage" for the general population and among young adults.
"If the goal is to prevent any infection, then it is likely that we will require multiple booster shots to sustain the high levels of antibodies needed to block infection. If the goal is to prevent all symptomatic infection, including those that are mild, then annual or even six-monthly vaccination may be needed as again, the baseline level of immune activity against Sars-CoV-2 will need to be high.
"If, however, the goal is to reduce the risk of severe COVID-19 that needs hospitalised management, then there is little indication that vaccine-induced immunity has waned to those levels in healthy young adults," said Prof Ooi.
Professor Dale Fisher, a senior consultant from the National University Hospital's infectious diseases division, noted that looking at T-cells and antibodies are "laboratory approaches" to understanding immunity.
"How much does that translate to reality? For this, we need clinical data such as infections, whether mild or severe, for different age groups and whether the patient has an infection after being vaccinated, and how long it has been since they were vaccinated," he added.
The vulnerable, such as seniors, are at higher risk, which is why a booster is recommended at five to six months after the primary vaccination series.
"We know at this time we see more mild infections, and there is no appetite to wait longer to see if severe infections emerge," he added.
Early studies from Britain also suggested that a booster jab will provide 80-85 per cent protection against Omicron, compared with 97 per cent against Delta. Though current vaccines are not a perfect match against Omicron, getting vaccinated does make it harder for Omicron to infect the body.
More antibodies are developed thanks to the booster, giving the body stronger defences against the virus.
https://www.straitstimes.com/singap...when-your-fully-vaccinated-status-will-expire
