Follow us on Telegram for the latest updates: https://t.me/mothershipsg

Thus far, Israel is the only country that has administered a fourth dose of the Covid-19 vaccine for people who are not immunocompromised, Health Minister Ong Ye Kun said in a Facebook post on Jan. 7.

Ong was highlighting several questions that had been asked following the multi-ministry taskforce's press conference on Jan. 5.

One of these questions was, "Now that we must get a third dose to get our vaccination status extended, does that mean there will be a fourth, fifth, sixth dose?"

In response, Ong said that it is "too early to answer that question".

He noted that in the case of influenza, an endemic disease, people take annual vaccines to protect themselves as the virus keeps mutating which necessitates a new dose every year.

Hence, whether a future Covid-19 vaccine dose is required depends on how fast protection from three doses wane, and whether the virus keeps mutating, he added.

Why is there a nine-month expiry date after two doses of the mRNA vaccines and three doses of the Sinovac/Sinopharm vaccines?

Here, Ong pointed out that the protection provided by the various Covid-19 vaccines will wane over time.

However, this can be restored with a booster dose which is recommended five months after the mRNA vaccines and three months after the third dose for Sinopharm or Sinovac.

As such, people aged 18 years and above who have completed a primary vaccination series should receive a booster dose of an mRNA vaccine no later than 270 days after the last dose, so to maintain their fully vaccinated status.

The minister also laid out the following calculations for people as an example:

"Say you got your Dose 2 of mRNA vaccine on June 1, 2021

Around 150 days or five months later, Nov. 1, 2021 – Eligible for booster

270 days or about nine months later, Feb. 26, 2022 – Get boosted by this date to be considered fully vaccinated

Day 271, Feb 27, 2022 – Fully vaccinated status will lapse if booster is not taken".

What about people who have recovered from a Covid-19 infection?

According to Ong, the immune system of people who have recovered without complications will have undergone a "strong stimulus" akin to "a fairly powerful vaccination shot."

Ong then noted that there were three scenarios of infection: being infected before vaccination, after vaccination or between the two doses of the Covid-19 vaccine.

In the cases of being infected before receiving both doses, or getting infected after both doses, Ong said that the person would be considered boosted.

Such people, therefore, do not need to rush for a booster.

He said, "Our experts tell us that under these scenarios, the immunity takes longer to wane, beyond nine months."

However, should a person from any of these two categories desire to go for a booster shot, it is safe to do so and the vaccination centres will also allow them to do so, he added.

As for a person infected in between doses, they will be considered fully vaccinated but not boosted.

Ong elaborated that was due to the timing between the two doses being three to four weeks.

Getting infected therefore means that the first dose and the infection are too close in timing together and will not be considered by the body as separate stimulants.

Hence, individuals who fall into this category will require a third dose to be considered boosted.

Follow and listen to our podcast here

Top photo by SATA CommHealth