Pfizer Booster Dose For 5-11 Yo Kids : What You Must Know!

Here is what you need to know about the Pfizer COVID-19 booster dose for 5-11 year old kids!


Pfizer Booster Dose For 5-11 Yo Kids : What You Need To Know!

On 17 May 2022, the US FDA officially approved the emergency use of the Pfizer-BioNTech COVID-19 vaccine as a booster dose for 5-11 year-old kids.

This Pfizer COVID-19 booster dose for kids is different from the COVID-19 booster dose for older children and adults in many ways, so let me summarise the key differences…

Lower Paediatric Dose

The dose of the Pfizer booster dose for 5-11 year old kids is only 10 micrograms (mcg). This is 1/3 of the dose used for adults and adolescents.

5-Month Dose Interval

The Pfizer paediatric COVID-19 booster dose for 5-11 year old kids is meant to be administered at least 5 months after the primary series is administered.

It does not mean your child must receive the booster dose exactly five months after completing the primary series. It just means the earliest your child should receive the booster dose is five months after receiving the primary series vaccine doses.

4th Dose For Some

For most children – the primary series consists of two doses, so the booster dose will be their third dose.

However, certain children are given three doses as their primary series vaccination :

  • who have undergone solid organ transplantation, or
  • who have been diagnosed with conditions that have an equivalent level of immunocompromise.

For these children, the booster dose will be their fourth dose of the vaccine.

10-Dose Vial

The booster dose for 5-11 years old kids uses the same Pfizer paediatric vaccine used in their primary series vaccination.

It is supplied in a 10-dose vial, with an orange cap and a label with an orange border, to differentiate from the higher-dose vaccine used for adults and adolescents.

Must Be Diluted Before Use

The content of the vial must be diluted with 1.3 ml of sterile 0.9% sodium chloride, to derive 10 doses of 0.2 ml in volume.

Healthcare workers must be aware of this dilution requirement, as the newer Pfizer vaccine with a gray cap (for individuals 12 years and older) no longer requires dilution.

Smaller Intramuscular Injection

The Pfizer booster dose for 5-11 year old kids is given as a 0.2 ml intramuscular injection. This is a smaller volume than the adult booster dose – 0.3 ml.

So parents should be aware that the paediatric booster dose has a lower volume, when observing their children’s vaccinations.

More Stable Formulation

The Pfizer’s paediatric vaccine, which is used for the booster dose, has an improved formulation that is more stable. For those who want to know what changed, Pfizer :

  • replaced the phosphate-buffered saline (PBS) with a Tris buffer
  • removed sodium chloride and potassium chloride from the buffer formulation

This improved formulation allows the vaccine to be kept in a normal refrigerator at 2°C to 8°C (35°F to 46°F) for up to 10 weeks, instead of just 4 weeks.

In addition, it will last longer – 12 hours, instead of just 2 hours – at room temperature (up to 25°C / 77°F), after being thawed.

Read more : Did Pfizer add heart attack drug to COVID-19 vaccine for kids?

9 Month Expiry Date

The Pfizer paediatric COVID-19 vaccine has a 9-month expiry date, from the printed manufacturing date.

Expiry Date
09/2021 31 May 2022
10/2021 30 June 2022
11/2021 31 July 2022
12/2021 31 August 2022
01/2022 30 September 2022
02/2022 31 October 2022
03/2022 30 November 2022
04/2022 31 December 2022
05/2022 31 January 2023

Mild Side Effects

The US FDA authorised the booster dose based on safety data from approximately 400 children who received the booster dose 5-9 months after completing their two-dose primary series.

They noted that the commonly reported side effects were pain, redness and swelling at the injection site, as well as fatigue, headache, muscle or joint pain and chills and fever.

This should be no different from the original safety data, which showed that the lower dose produced fewer side effects, with no severe side effects noted. They were mostly :

  • pain at injection site : 71-74%
  • headache : 54-61%
  • fatigue : 60-66%
  • muscle pain : 27-41%
  • chills : 25-40%
  • joint pain : 13-22%
  • fever : 7-17%

Side note : It is interesting to note that even the placebo causes common symptoms like fatigue, headache and muscle pain. This shows just how important it is to conduct a randomised controlled trial.

Safer Than Adult Dose

The much lower dose appears to ameliorate, if not eliminate, the risk of myocarditis / pericarditis that was highest in adolescents and young adults.

There were no cases of pericarditis or myocarditis in the initial Pfizer study that involved over 2,260 children, through approximately 3 months of follow-up after Dose 2.

After 8.7 million doses were administered in the US (up to 19 December 2021), the US CDC noted that :

  • VAERS received 4,249 adverse event reports (0.049% of doses)
  • 4,149 (97.6%) of those adverse events were not serious
  • Of the remaining 100 serious adverse events, 29 were fever, 21 were vomiting, and 15 were increased troponin.
  • Only 11 verified cases of myocarditis were identified – 7 recovered completely, and 4 were recovering at the time of the report.

Based on those results, the risk of myocarditis was 1 in 791,000 doses – much lower than the risk of myocarditis in young adults (1 in 50,000).

For a better perspective of the risk of developing myocarditis, I created this comparison table for you :

Myocarditis Risk Per Million People Difference
COVID-19 Patient 450 +2208%
Pfizer Vaccine
(Adult Dose)
20 +2.6%
Pfizer Vaccine
(Paediatric Dose)
2.5 -87%
Normal Population 19.5 Baseline

As you can see, the risk of developing myocarditis is MUCH higher if your child gets infected with COVID-19, compared with getting the Pfizer vaccine.


Pfizer Booster Dose : Should Your 5-11 Yo Kids Get It?

While the US FDA did not reveal how much of a boost in antibody the Pfizer booster dose will give your 5-11 year old children, there is a definite boost in antibody level.

That said, antibody levels are not an accurate assessment of an individual’s immunity against COVID-19.

Studies have shown that additional vaccine doses induces the memory B cell and T cell responses to an actual COVID-19 infection.

While that may not prevent infection, especially by the highly-infectious Omicron variants, the improved B cell and T cell responses will greatly reduce the severity of any COVID-19 infection.

Therefore, I would definitely recommend giving your kids the Pfizer booster dose, if it is made available to them.


Please Support My Work!

Support my work through a bank transfer /  PayPal / credit card!

Name : Adrian Wong
Bank Transfer : CIMB 7064555917 (Swift Code : CIBBMYKL)
Credit Card / Paypal :

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.

He continues to devote countless hours every day writing about tech, medicine and science, in his pursuit of facts in a post-truth world.


Recommended Reading

Go Back To > Health + Science | Tech ARP


Support Tech ARP!

Please support us by visiting our sponsors, participating in the Tech ARP Forums, or donating to our fund. Thank you!

Leave a ReplyCancel reply