Booster shots, additional COVID-19 vaccine doses in PH: What you need to know

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Metro Manila (CNN Philippines) — The government is rolling out COVID-19 booster shots for all adults over 18 years old beginning Dec. 3, as well as additional doses for individuals with weakened immune system to give them additional protection nine months since the country launched its nationwide vaccination drive.

CNN Philippines answers your questions on booster shots and additional doses, who are eligible to receive these, and how you can avail of these.

What's the difference between booster shot and additional dose?

Booster shots are given to those whose immunity is decreasing over time after completing their COVID-19 vaccination.

Additional COVID-19 vaccine doses are given to individuals who never reached the ideal immune response level due to their health problems, namely people with underlying illnesses.

A person can only receive one booster or additional shot. It is purely voluntary.

Who can avail of booster shot and additional dose?

Booster shots are given to fully vaccinated adults over 18 years old six months after completing a two-dose vaccine and three months after taking a single dose vaccine. Healthcare workers who received their primary doses abroad can also get their booster shots in the Philippines.

Additional doses will be given to immunocompromised adults.

What vaccine should I get?

The DOH has approved administering a single dose of Pfizer, Sinovac, and AstraZeneca, and half the regular dose of a Moderna shot as booster or extra dose.

It shall be given at least six months after if they received Pfizer, Moderna, Sinovac, Sputnik V, and AstraZeneca as their first series, or three months after if they got the single-shot Janssen.

Am I getting the same vaccine brand or a different one?

The DOH said one can opt to use the same vaccine brand (homologous vaccine) or a different one (heterologous vaccine) from the initial series received.

However, those who got Sputnik V and Janssen as their first series cannot receive the same brand as their booster for now. This is because there is not enough supply of Sputnik V vaccine and Janssen has yet to apply for an amendment to its emergency use authorization to include booster shots in its regimen, officials said.

Which vaccine brands can I mix? Is it safe?

If the vaccinee opts to get a different brand as their booster, they may receive the following combination:

- Sinovac: AstraZeneca, Pfizer, Moderna

- AstraZeneca: Pfizer, Moderna

- Sputnik V: AstraZeneca, Pfizer, Moderna

Janssen: AstraZeneca, Pfizer, Moderna

- Pfizer: AstraZeneca, Moderna

- Moderna: AstraZeneca, Pfizer

While the vaccinees have options, Health Undersecretary Maria Rosario Vergeire said those who initially got the mRNA vaccines made by Pfizer and Moderna are "not recommended" to receive the inactivated vaccine (ex. Sinovac) as their booster shot.

The DOH official also said those who received two doses of AstraZeneca can be given a shot from the same brand as their booster, but it should be used with precaution due to a possible efficacy issue. She said those inoculated with vector-based vaccines such as AstraZeneca are recommended to get a vaccine from a different brand for their boosters.

But Vergeire cautioned that with heterologous vaccinations, studies point out that more adverse reactions are expected especially with the Pfizer and Moderna vaccines.

Meanwhile, "with homologous vaccinations, there are more consistent studies with regards to its safety with a similar efficacy versus severe or critical COVID-19," she added.

Vergeire further said it may be best for those who experienced adverse reactions to vaccines to receive a homologous series due to its more consistent safety profile.

Vaccine recipients with "higher risk for adverse reaction" such as the elderly, people with underlying illnesses, and those prone to blood clots, myocarditis, and anaphylaxis should consult their attending physicians for the recommended boosting strategy, she added.

What are the benefits?

Vulnerable populations are highly encouraged to get additional shots, according to health experts.

"If your risk is high, if you are in A2 or A3, or your exposure is high — A1 frontliner, we are giving the option," infectious diseases expert Dr. Edsel Salvana previously said in a town hall.

Salvana added that getting a booster dose is voluntary "precisely because we do not know what is the added protection versus the potential risk of side effects with either the homologous or heterologous vaccines." But he noted that boosters might work for certain populations.

Dr. Anna Ong-Lim had a similar view.

"Kung A1 tayo at nabibilang sa mga grupong iyon (senior citizens, immunocompromised individuals), those groups we would encourage — avail of this opportunity now kasi mukhang kakailanganin nila," she said.

[Translation: If we are part of A1 and also belong to the groups of senior citizens, immunocompromised individuals, we would encourage - avail of this opportunity now because they might need it.]

The protection provided by COVID-19 vaccines wane faster in senior citizens and immunocompromised individuals than the general population, Department of Science and Technology's vaccine expert panel head Nina Gloriani said in a government briefing.

Gloriani said data showed the immunity of senior citizens and people with underlying medical conditions diminishes after three to five months while that of the general population, which she described as healthy people aged 18 to 60, wanes after six to 10 months.

Where can I get it and what do I need to bring?

Vergeire said any vaccination site with enough supplies can administer booster and additional shots. They need to bring their vaccination card and valid ID. Those who are immunocompromised need to obtain a medical clearance from their doctor.

Vaccination sites are urged to set up different lanes for the primary series and the extra shot to avoid confusion.