Claims about changes to Pfizer vaccine for children miss important details

24 November 2021
What was claimed

Pfizer has changed the formulation of its Covid-19 vaccine for children aged five to 11 to include an ingredient used to stabilise heart attack patients.

Our verdict

The FDA recently approved the inclusion of tromethamine in paediatric doses of Pfizer’s Covid-19 vaccine. It was included to extend the vaccine’s shelf life, and is not currently used in the UK. It is used to treat a condition which may result from illness following a heart attack.

An article, shared on Facebook, claims Pfizer has changed the formula of a Covid-19 vaccine for children to include a medication that “stabilises people suffering a heart attack”.

The article says the vaccine for five to 11-year-olds includes tromethamine, which is associated with a number of potentially serious side effects.  

Tromethamine was recently added to the Pfizer vaccine for five to 11-year-olds in the US, and it is a medicine that can be used to treat other conditions which a heart attack may cause. But its inclusion has been approved by the US to increase the shelf life of the vaccine while it is refrigerated. 

Side effects mentioned in the article are rare and associated with doses much higher than the amount in the Pfizer vaccine. 

In the UK, tromethamine is not currently included in the Pfizer vaccine. At the time of writing, only children aged 12 and over are eligible for any Covid vaccines in the UK. 

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What is tromethamine?

Tromethamine (also known as Tris) is a type of solution called a buffer that maintains the pH level of medicines and improves their stability when in use. 

It is also used as medication to treat metabolic acidosis, which makes the blood in the body too acidic. This condition can occur from a number of causes including cardiac arrest (which can occur following a heart attack).  

Why is tromethamine in the Pfizer vaccine?

In October, the US Food and Drug Administration (FDA) granted emergency approval for the use of a new vaccine, containing tromethamine, for five to 11-year-olds. 

While the article doesn't explicitly suggest why tromethamine has been added to the vaccine, and instead frames this as a question, it does repeatedly talk about the risk of heart complications as a result of the vaccine. However, while there have been reports of some cases of myocarditis and pericarditis (inflammation relating to the heart) following vaccination with both the Pfizer and Moderna vaccines, these are very rare and were not related to the change in this Pfizer vaccine’s formula.

Pfizer confirmed to Full Fact the new formula was created to extend storage time of its vaccine by up to 10 weeks at 2-8°C in common refrigerators (its previous formula could only be refrigerated for a month).

In a press conference from October, the director of the FDA’s Center for Biologics Evaluation and Research Dr Peter Marks said tromethamine was “commonly used as a buffer in a variety of other FDA approved vaccines and biologics including products for use in children.

“The FDA evaluated manufacturing data to support the change in this inactive ingredient and concluded it did not impact the safety or effectiveness of the product.”

Pfizer confirmed to Full Fact that it intends for tromethamine to be included in adult doses of the vaccine, although this has not been approved by the UK’s Medicines and Healthcare products Regulatory Agency at the time of writing. 

What about the side effects?

The article claims there are a number of side effects associated with tromethamine including respiratory depression (slow and ineffective breathing), IV thrombosis (vein inflammation that can cause blood clots, following IV use) and hypoglycemia (a low blood sugar condition that can cause seizures, most common among people with diabetes).

However, as Health Feedback states, these are side effects associated with metabolic acidosis patients who receive intravenous injection of tromethamine solution up to half a litre at a time.

By comparison, the Pfizer Covid-19 vaccine dosage for five to 11-year-olds is considerably smaller at only 0.2ml (of which tromethamine is just one component). 

We have previously written about misreporting vaccine side effects experienced by children.

Vaccines have been tested for safety

The article also questions whether these recent changes mean the previous Pfizer vaccines were unsafe and says there claims there is "overwhelming evidence against the safety of the vaccine".

Pfizer confirmed to Full Fact that the change was made to ensure its vaccines had a longer shelf life, with no other changes to its manufacturing process, raw material, mRNA, lipids or suppliers in the manufacturing of the drug substance and lipid nanoparticles. 

The FDA has stated vaccine trials, which initially included more than 4,600 participants aged five to 11, showed side effects were “generally mild to moderate in severity and occurred within two days after vaccination, and most went away within one to two days.”

It added: “The FDA’s model predicts that overall, the benefits of the vaccine would outweigh its risks in children 5 through 11 years of age.”

FDA documents state the addition of tromethamine is not considered “clinically significant”. It is used in a number of medicines including the UK-authorised formula of the Moderna vaccine (where it is listed as Trometamol). 

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