Now that both the Pfizer and Sinovac vaccines are approved for 5-11 year old kids, some parents are wondering – which is the better vaccine for their child?
Here is a quick summary of both vaccines, as well as their safety and their efficacy against COVID-19!
Pfizer vs. Sinovac Child Vaccine : Different From Adult Vaccines?
One of the first questions parents ask me is if the Pfizer and/or Sinovac vaccine for 5-11 year-old children are the same, as the adult vaccines.
The Pfizer vaccine for 5-11 year old children is an improved formulation based on the adult vaccine, while the Sinovac vaccine is exactly the same for both adult and children.
Here is a simple and quick comparison :
|Formulation||Improved with Tris buffer
More stable, longer storage
|No. of Doses||2 Doses
1/3 of adult dose
Same as adult dose
2/3 of adult vaccine
Same as adult vaccine
|Dose Interval||8 Weeks *
5 weeks longer
Same as adult vaccine
* In some countries only, Pfizer still recommends the original 3-week dose interval
Pfizer vs. Sinovac Vaccine : Which Is Better For Your Child?
Pfizer Child Vaccine Efficacy : 90.7%
The Pfizer bridging study showed that their lower-dose paediatric vaccine was 90.7% efficacious in preventing symptomatic COVID-19 infection.
Their study also showed that the Pfizer paediatric vaccine produced high neutralising antibody titres against the Delta (B.1.617.2) variant at 1 month after Dose 2.
After Dose 2
|Geometric Mean Titres
Sinovac Child Vaccine Efficacy : Unknown
Back in October 2021, the Malaysia Ministry of Health (KKM) ran a Phase 3 clinical trial to determine the efficacy of the Sinovac COVID-19 vaccine for children 3-11 years in age.
However, they did not reveal what was the efficacy of the Sinovac COVID-19 vaccine for the 5-11 year old age group, or how it performed against the Omicron variant.
We do know that the adult dose was only 50.4% efficacious in preventing symptomatic COVID-19 from the original SARS-CoV-2 virus, and that it has zero efficacy against the Omicron variant (see link and table below).
It seems very improbable that the same vaccine would impart better efficacy in children, more so against the Delta or Omicron variants.
|Seropositive Rate||MN Titer (GMT)|
Pfizer Is Definitely Better Than Sinovac For Your Child
Until there are good peer-reviewed Phase 3 results of the Sinovac CoronaVac vaccine for 5-11 year-old children, I believe it is far more prudent to vaccinate your child with the Pfizer COMIRNATY paediatric vaccine.
At least the Pfizer paediatric COVID-19 vaccine has been proven in a Phase 3 trial to be 90.7% efficacious in preventing symptomatic COVID-19 infections in 5-11 year-old children.
It is highly unlikely that even the adult dose of the Sinovac vaccine can impart anything close to its original 50.4% efficacy against the ancestral COVID-19 virus, and it seems very likely to perform poorly against the Delta and Omicron variants.
If you want the best protection for your child, get the new Pfizer vaccine for kids. Only consider the Sinovac vaccine if your child has an adverse reaction to the first dose of the Pfizer vaccine.
Pfizer vs. Sinovac Vaccine : Which Is Safer For Your Child?
This is also another question that many parents are asking. Everyone is worried about COVID-19, but no one wants their child to be “injured” by a vaccine.
There isn’t a straight answer, because safety has to be balanced against the risk of injury from a breakthrough infection – getting COVID-19 despite being vaccinated.
Sinovac Vaccine : Fewer Side Effects But Low Efficacy
The Sinovac vaccine is no doubt a very safe vaccine, with fewer complaints of side effects. Generally, they include pain and swelling at the injection site, fever, headache, nausea, diarrhoea, joint pain, cough, chills, sore throat and runny nose.
While parents will be relieved to hear that, I must point out that this is because the Sinovac vaccine generates a much weaker immune response. Even with an aluminium hydroxide adjuvant to boost the immune response, its efficacy is relatively poor at 50.4% against the original COVID-19 virus.
Pfizer Vaccine : More Side Effects But Much Higher Efficacy
The Pfizer vaccine is also a very safe vaccine, with rare risks of anaphylaxis and myocarditis in young adults and adolescents. The risk is not much higher than with other vaccines, as my table of data from the massive SAFECOVAC study shows :
- Pfizer : 1 in every 1.11 million doses
- AstraZeneca : 1 in every 1.43 million doses
- Sinovac : 1 in every 2 million doses
|Age Groups||Myocarditis Events
(Per Million Doses)
|Over 30 Years||1.0||NA||0.6|
|30 Years + Younger||0.87||NA||0.49|
We must also remember that myocarditis is a condition that can affect anyone who suffers a viral infection, and is also seen with a COVID-19 infection.
In fact, you are far more likely to get myocarditis from a COVID-19 infection than either the Pfizer or Sinovac vaccine.
Here is my comparison of the myocarditis risk of triple vaccination (two doses + booster) versus a single COVID-19 infection.
No matter how you slice and dice the results, it is very clear that the risk of myocarditis is GREATEST with a single COVID-19 infection, than it is with THREE doses of the Pfizer, AstraZeneca or Sinovac vaccines.
If you are worried about your child getting myocarditis, you should definitely protect him/her using the best COVID-19 vaccine you can get, and that would be the Pfizer paediatric vaccine.
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Dr. Adrian Wong has been writing about tech and science since 1997, even publishing a book with Prentice Hall called Breaking Through The BIOS Barrier (ISBN 978-0131455368) while in medical school.
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