Lighter boosters 'just as efficacious'

Lighter boosters 'just as efficacious'

ON THE RECORD: There are pros and cons from having new intradermal shots, writes Karnjana Karnjanatawee

A medical worker prepares a dose of vaccine against Covid-19 at Kasetsart University, Bangkok, on Feb 2, 2022. (File photo: Varuth Hirunyatheb)
A medical worker prepares a dose of vaccine against Covid-19 at Kasetsart University, Bangkok, on Feb 2, 2022. (File photo: Varuth Hirunyatheb)

The vaccination centre at Bang Sue Grand Station started offering people the option of a lighter dose for their third or fourth shot from Feb 1. The newly added options are an intradermal (under the skin) injection and a half-dose intramuscular injection.

Dr Mingkwan Wichaidit

In an interview with the Bangkok Post, Dr Mingkwan Wichaidit, director of the Institute of Dermatology of the Department of Medical Services, Ministry of Public Health, and director of the vaccination centre, said the intradermal injection requires only one-third of a normal dose.

The normal dose for a shot of Pfizer -- the main vaccine administered by the centre today -- is 30 microgrammes (mcg) per dose, whereas the intradermal injection uses just 10mcg. The lighter intramuscular shot requires 15mcg per dose.

"The efficacy of both methods is as high as having a full dose administered," Dr Mingkwan said.

The decision to add the two lighter-dose options was approved by the Department of Disease Control's sub-committee on promoting disease immunity at the end of December.

They reviewed numerous studies in Thailand and abroad and found no significant difference in statistics in term of immunity levels or the period before immunity declines among all three methods of administering the booster shots.

What are the pros and cons of having the intradermal shot?

The benefit of administering a 10mcg dose under the skin is that we use less vaccine so there is a lower chance of experiencing side effects like fever or fatigue, while the level of immunity and period of the protection is as high as having full doses.

However, recipients may develop some form of skin irritation for one or two days before they recover.

I also took the intradermal vaccination for my fourth shot. Personally, I can say it hurts more than the third shot of a full dose of the intramuscular injection. But I did not develop any side effects.

Why are you offering this option now? Is Thailand experiencing a shortage of vaccines?

We have more than enough vaccines right now. In fact, the intradermal option was raised around the middle of last year when the country faced a vaccine shortage, but the sub-committee on promoting disease immunity needed to review all related papers before coming to a conclusion. We had to be sure of its efficacy before we introduced [these two new options].

Can people have the intradermal vaccination for their first or second shot?

That vaccination method is recommended for booster shots. For those who have not received any vaccine, we have to follow the prescribing information of the vaccination providers, which are full doses for the first two shots.

Is this method applied only to mRNA vaccines?

Based on the papers that the sub-committee reviewed, the intradermal vaccination can be applied to any type of vaccine whether it is viral vector or mRNA. It also depends on what vaccine the government is providing right now.

At the vaccination centre in Bang Sue, we offer Pfizer for the booster shot because most of the people who get vaccinated with us received two shots of AstraZeneca. We also have AstraZeneca as an option.

How can people get the intradermal or half-a-dose vaccination?

They need to tell our staff when they arrive at the centre (based on their booking queue number). We recommend those who want a lighter dose enter at Gate 2 and turn left. If you turn right, then you will approach the normal stations for full doses. If people need more information, we have doctors on site to offer help.

How many people have chosen the lighter jabs?

On the first day, we saw about 2,700 people vaccinated using both (newly added) methods. The total number of people vaccinated that day was about 31,000, so it works out at about 10%.

On the second day, the number rose to over 4,000. On Feb 3, after we'd opened for half a day, more than 4,000 people were administered both methods. The number keeps rising as more people learn about the new options.

How long will the centre provide these alternative methods?

As long as the centre remains open. We forecast that we can complete offering the third or fourth shots around the end of March or by April 8. We may halt the service over Songkran.

But there are still people who received two doses of mRNA vaccine, and they will need a booster in April or May.

Furthermore, our centre will soon open for kids aged 5-11 years so they can get their first Covid-19 vaccine from this coming Thursday. They will need a second shot after eight weeks, or around the middle of April.

How many people have been vaccinated at your centre?

It opened last May. Since then, we have administered about 4.5 million shots or 30,000 a day. I hope our centre can be closed within this year. Don't be alarmed if the facility shuts down because that will be good news -- meaning we don't need to provide mass vaccinations anymore.


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