COVID-19 booster shots in PH: What you need to know

Metro Manila (CNN Philippines)— The Philippine government is rolling out COVID-19 booster shots for all adults over 18 years old to increase their protection against the coronavirus disease and emerging variants.

CNN Philippines answers your questions on booster shots, when you can receive them, their benefits, and where they stand against variants.

What is a booster shot and who can get it?

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

They are given to fully vaccinated adults three months after completing a two-dose vaccine and two months after taking a single-dose vaccine. The interval between the primary series and booster was shortened by the Food and Drug Administration beginning Dec. 22 amid the emergence of the more transmissible Omicron coronavirus variant, which rapidly became the most dominant variant in the United States 20 days after its detection.

A person can only receive one booster shot months after completing their primary series.

It is purely voluntary but highly encouraged by health experts amid the detection of new coronavirus variants. Senior citizens and immunocompromised individuals are urged to get it as early as possible since the protection provided by COVID-19 vaccines wane faster in vulnerable sectors.

Those below 18 years old are not yet allowed to get booster shots.

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

The Department of Health said booster shots shall be given at least three months after receiving AstraZeneca, Gamaleya Sputnik V, Gamaleya Sputnik Light, Moderna, Pfizer, Sinopharm, and Sinovac shots, or two months after the single-shot Janssen.

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 received Sputnik V, Sputnik Light, and Janssen as their first series cannot receive the same brand as their booster for now, so they have to get a different vaccine brand.

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:

- AstraZeneca: Pfizer, Moderna, Sputnik Light

- Gamaleya Sputnik V: AstraZeneca, Pfizer, Moderna

- Gamaleya Sputnik Light: AstraZeneca, Pfizer, Moderna

- Moderna: AstraZeneca, Pfizer, Sputnik Light

- Pfizer: AstraZeneca, Moderna, Sputnik Light

- Sinopharm: AstraZeneca, Moderna, Pfizer

- Sinovac: AstraZeneca, Pfizer, Moderna, Sputnik Light

- Janssen: AstraZeneca, Pfizer, Moderna

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? How do they stand against variants?

Vaccine makers have known for months now that the immunity vaccines elicit against COVID-19 can go down over time, leading to the need for a booster dose. Vaccine experts here and abroad agree that the boosters appear to restore immunity to where it was initially and improve protection against emerging coronavirus variants.

Two separate studies from Israel showed booster doses of Pfizer/BioNTech's coronavirus vaccine reduced infections tenfold and reduced COVID-19 deaths by 90%.

The vaccine expert panel in the Philippines recommended that fully vaccinated adults be given earlier access to booster shots to due to the growing threat of the Omicron variant, which is seen to increase the risk of reinfection.

Pfizer/BioNTech announced that preliminary lab studies show a third dose of its vaccine can improve protection against Omicron, while Moderna also said that preliminary data suggests its booster shot increased antibody levels against the Omicron variant.

When can I get my booster shot if I tested positive for COVID-19?

The DOH in January 2022 set three criteria before a person who recently tested positive for COVID-19 can avail of their booster shot to get additional protection.

1. You have to complete your isolation period. For fully vaccinated patients who are asymptomatic or with mild symptoms, it will be after a 7-day isolation. It can take up to 21 days if a person experienced severe symptoms.

2. You need to have a normal body temperature for 24 hours even if you don't take medicine for fever.

3. Your respiratory symptoms have significantly improved.