With Singapore bracing itself for a large Omicron infection wave, a person’s fully vaccinated status will lapse nine months after the last dose of his primary vaccination series, in a new policy shift announced on January 5.
These are some frequently asked questions.
Q: How long does my fully vaccinated status last if I had been vaccinated with an mRNA vaccine? When do the rules come into effect?
A: If you are 18 and older and have been vaccinated with mRNA jabs, you will need to get your booster dose nine months after your second dose to retain your fully vaccinated status. February 14th will be the effective date.
To maintain your fully vaccinated status, you must get your booster dose if your second dose was not received before May 20, last year.
Q: How long will my fully vaccinated status last, if I have taken the Sinovac and Sinopharm vaccines?
A: You are considered fully vaccinated only after three doses. To be considered fully vaccinated, you will need to take a booster dose nine month after your third dose.
Q: Do I still need to take a boost dose after I have recovered?
A: At this time, booster doses are not required. If you are unvaccinated/partially vaccinated, you will still need to receive a dose or two of Sinovac or Sinopharm.
If you have taken two doses Sinovac and then got Covid-19, you will need to get one more Sinovac dose or Sinopharm dose after recovery to be fully vaccinated. Your additional dose should be received no later than 28 days after your Covid-19 diagnosis.
Those with mixed vaccine combinations should refer to this link.
Anyone who has been tested positive for antigen rapid but not confirmed by polymerase chain reactions will need to be given a booster dose.
According to the Ministry of Health’s website, there are no additional safety concerns with taking the booster jab if you had unknowingly recovered from a past infection.
It stated that there is no evidence to suggest that vaccinations of those who have been vaccinated for autoimmune disorders, overstimulation or other safety concerns.
Q: What is the rationale behind the nine-month expiry date of one’s fully vaccinated status? My protection against Covid-19 will then diminish. Do we need multiple booster shots?
A: Associate Professor Hsu Li Yang, vice-dean of global health and programme leader of infectious diseases at the National University of Singapore’s Saw Swee Hock School of Public Health, said a number of studies in several countries, including Singapore, show that in most vaccinated people, their neutralising antibodies start falling after two to three months. This means that the protection against infection would decrease after a few months.
“Protection against severe disease, hospitalisation and death has thankfully, lasted longer, no doubt because of T-cells (which kill virus-infected cells) and the adaptive immune system,” he added.
The adaptive immune reaction refers to the second layer in immune defense that the body develops. It can take several days or weeks for it 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,” said Prof Ooi.
“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.”
Credit: The Straits Times
Professor Dale Fisher, a senior consultant at 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.
Seniors, who are most vulnerable, are at greater risk. Therefore, boosters should be administered at least five to six month after the initial 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 British studies have shown that booster shots can provide between 80 and 85 percent protection against Omicron. This is in contrast to the 97% protection provided by Delta. Omicron can infect the body even though current vaccines do not protect it completely. However, it is easier to get vaccinated.
The booster increases the production of antibodies, which makes the body more resistant to the virus.
Q: Is it better to take my booster dose nine months after my first dose than at the fifth-, sixth-, or sixth-month mark.
A: Prof Fisher said it is not completely clear, though there is general consensus that a booster at five to six months is recommended for those at risk of developing severe disease.
“In younger age groups, it is more contentious as their risk of severe disease is less, and this is why a pragmatic longer period is being chosen in Singapore, I believe,” he added.
The Expert Committee on Covid-19 Vaccination recommends that people receive their booster dose at about five months after the last dose of their primary vaccination series, or as soon as possible thereafter to maintain good protection against Covid-19.
Q: What is the role of booster jabs in other countries?
A: Israel was the first country to roll out booster jabs for those who took the Pfizer vaccine, and mandates that those 12 and older must take a booster dose to be considered fully vaccinated. It is now considering a second booster dose for those 60 and older.
The United States Centres for Disease Control and Prevention (CDC) said three doses of Pfizer-BioNTech’s or Moderna’s vaccines should be considered “up-to-date” inoculations, and that Johnson & Johnson recipients should receive a second dose, preferably of Moderna or Pfizer-BioNTech, to also be considered up to date. The CDC expanded its recommendation for booster shots in order to include all Americans over 12 years old.
Though the CDC did not change the technical definition of “fully vaccinated’ – two doses of an mRNA vaccine or one dose of the J&J vaccine – the agency did recommend that people “stay ‘up to date’ by receiving any additional doses they are eligible for to ensure optimum protection”.
In Britain, boosters are available to all above 18, three months after their second dose.
This article was first published in The Straits Times.
Source: Her World