Metro Manila (CNN Philippines, November 18) — A vaccine expert on Thursday explained why Sinovac’s COVID-19 vaccine is not recommended as a boosters for healthcare workers who initially got Pfizer and Moderna shots.
“Ang basehan niyan ay immunogenicity studies. Napakataas po ng [antibody] level ng mga bagong platforms like messenger RNA, adenovirus at medyo mababa po iyong sa inactivated,” Department of Science and Technology’s vaccine expert panel head Nina Gloriani said in a Laging Handa briefing.
[Translation: That is based on immunogenicity studies. Messenger RNA (mRNA) and adenovirus vaccines made using new platforms elicited very high antibody levels while inactivated generated quite low.]
“So, we just deemed it na kailangan kung bagong platform ang nareceive ninyo iyon narin ang booster,” she added.
[Translation: So, we just deemed it is necessary that if you received a vaccine developed using a new platform, you should get the same as booster.]
The shots made by Pfizer and Moderna are mRNA vaccines, and they have previously shown high efficacy – well over 90% – in clinical trials involving tens of thousands of participants, with limited side effects.
Sinovac – the first to be rolled out in the country – is called an inactivated vaccine. This vaccine type uses a killed form of SARS-CoV-2, one of the oldest and tried-and-tested methods of prompting an antibody response.
Fully vaccinated healthcare workers can now choose which COVID-19 vaccine to receive as a booster shot, provided the one they prefer is available at vaccination sites. Approved to be used as booster shots are Sinovac, Pfizer, Moderna, and AstraZeneca vaccines.
Those who originally received Sinovac, Pfizer, Moderna, or AstraZeneca can opt to be injected with the shot made by the same brand or a different one.
But the Department of Health earlier said those who originally got the mRNA vaccines are “not recommended” to receive an inactivated vaccine as their booster shot.
Gloriani also said those who received two doses of AstraZeneca can still be given a shot from the same brand as their booster, but it should be used with precaution. She said those inoculated with vector-based vaccines such as AstraZeneca is recommended to take a vaccine from a different brand for their booster due to a possible efficacy issue.
Meanwhile, healthcare workers who initially got Sputnik V or Janssen vaccine can pick AstraZeneca, Pfizer, or Moderna.
Gloriani said Sputnik V is not yet being offered as a booster shot due to supply issues while Janssen has yet to apply for an amendment to its emergency use authorization to include booster shot in its regimen.
