Should I be getting a Covid Booster Jab?

Are you wondering why there is a need to get a booster vaccine? Does the need for getting a booster mean the vaccines do not work?

Hopefully this article will help clarify some of those questions.

What is a vaccine booster? How does it work?

Vaccines work by triggering our immune cells to produce antibodies and other molecules which protect against infection, but these slowly drop with time. It leaves a pool of “memory” immune cells that have been trained to target and eliminate future infections by that particular invader or pathogen.

A booster dose can enhance your body’s immune memory against the targeted pathogen, such that in the event of actually encountering it, your body produces a stronger and faster immune response that protects against its invasion.

Do I need to get a vaccine booster against COVID-19?

According to MOH guidelines at the time of writing, a booster dose for the COVID-19 vaccine is currently recommended for the following groups of people, 6 months following their primary series vaccinations:
1) Persons aged 30 years and above

2) Residents of aged care facilities, regardless of age

3) Persons younger than 30 working in healthcare/frontline sectors

4) Persons who are immunocompromised and have received a 3-dose enhanced primary series

Why do I need to get a vaccine booster against COVID-19?

Vaccination against COVID-19 works. Research studies have been ongoing since the start of the COVID-19 pandemic, to ensure the safety and efficacy of vaccines that have been rolled out world wide. Studies have consistently shown that vaccination effectively protects against infection by the virus, serious disease and hospitalisations, meaning that most vaccinated individuals have mild or no symptoms when infected. Vaccinated individuals also appear to recover faster than unvaccinated individuals.

Here in Singapore, local observational data has shown that almost all fully vaccinated individuals experience only mild to moderate disease when infected, except for those with underlying medical conditions that increase their susceptibility to serious disease. According to MOH data, percentage of unvaccinated COVID-19 patients who became severely ill or died was 6.7%, versus 0.9% for those fully vaccinated, as of data on 5th September 2021. (1) Data from the United States also show that hospitalisation rates are 10-22x higher in unvaccinated adults relative to vaccinated adults. (2)

However, more recent studies are starting to show that the protection against contracting the virus appears to decrease with time. One study showed early evidence that efficacy of the Pfizer-Biontech mRNA vaccine dropped from an initial 96% at 2 months post-vaccination, to 84% after 6 months. Efficacy against severe disease however, maintained at 97% at 6 months. (3) This decline may also be due to newer variants of the virus emerging, such as the Delta variant. The decline in immunity is also shown to be greater in adults over the age of 65.

A study performed in Israel confirmed that rates of COVID-19 infection and severe infection were significantly lower after receiving a booster dose of an mRNA vaccine. (4) Both Israel and the US have similarly been commencing booster doses of COVID-19 vaccines, targeting those aged 60 and older, and younger adults with medical conditions or higher risk of exposure to the virus (e.g. frontline work). (2) A growing list of countries have also started booster regimes – including China, Russia,United Arab Emirates and Germany.

Receiving a booster not only brings individual benefit, enhancing personal immunity which reduces your own likelihood of infection and severe disease (particularly those above 50 years old), it also reduces transmission risk to others. This particularly benefits the more vulnerable such as elderly, and those with underlying medical conditions who may be immunocompromised.

Can I mix vaccines?

As per MOH guidance, persons may receive either brand of the Pandemic Special Access Route (PSAR) mRNA vaccines as a booster (i.e. Pfizer-BioNTech/Comirnaty or Moderna vaccines). (5) There are currently no recommendations to take a non-mRNA vaccine as a booster (e.g. Sinovac, Sinopharm) after receiving the first two doses of mRNA vaccines.

On the other hand, MOH has advised that “persons who had received two doses of Sinovac/Sinopharm under HSA’s Special Access Route are recommended to receive a dose of the PSAR mRNA vaccine as a booster dose, if they are not contraindicated to receive the mRNA vaccines.” This is likely due to the increased efficacy of mRNA versus the Sinovac/Sinopharm vaccines.

In a study recently published, it was found that mixing of three different COVID-19 vaccines (Pfizer-BioNTech, Moderna, Johnson & Johnson/Janssen) was safe – where the booster dose was of a different brand to the initial two-series vaccines. The following results were also found: after a primary Moderna series, those receiving a Moderna or Pfizer booster showed benefit with no significant difference. After a primary Pfizer series, the greatest benefit was from a Moderna booster, but a Pfizer booster helped also. (6)

What if I have already received the Sinovac/Sinopharm vaccines?

The Multi-Ministry Taskforce (MTF) announced on 23 October 2021 that the Sinovac-CoronaVac COVID-19 vaccine would be included in the National Vaccination Programme (NVP). (7) It is given as a 3-dose primary vaccination series, where the second dose is given 28 days after the first dose, and the third dose should be given 90 days after the second dose. Persons who have completed the 3-dose regimen will be considered fully vaccinated. This is due to a noted drop in antibody levels after only two doses, returning to pre-vaccination levels by six months, in both younger and older adults.

Persons receiving the Sinopharm vaccine are similarly advised to receive a third dose of the vaccine as a 3-dose primary series, with the same schedule as Sinovac.

Please speak to any of our doctors in Healthsprings if you have more questions or concerns regarding receiving a COVID-19 vaccination or booster.