We often gloss over the extensive list of ingredients found on food labels, casually crunching on a pack of Doritos and washing them down with Red Bull without a second thought. However, unlike a packet of crisps or can of energy drink, the ingredients which make up vaccines have come under major scrutiny. Each component has been extensively reviewed and tested for their safety and use in humans. So, are vaccines safe, or should I worry about the heavy metal being injected into my veins?
The essential component to any vaccine is the active ingredient: the sample of a pathogen for which the vaccine is acting against. The other components are not only found in tremendously small quantities, but quite often they occur in our bodies naturally. Interestingly, constituents used in the manufacturing process of vaccines are also noted as ingredients – despite being absent or in trace amounts in the final product. A lengthy list of confusing ingredients may trigger worry when the truth is that each item is there with purpose and safety in mind.
A worry over metal
The thought of metal entering our bodies is often a case put forward by the anti-vax audience. Mercury is one such metal that is readily discussed in such context. In actuality, mercury in vaccines is found as the compound Thimerosal – a preservative used to prevent contamination of opened multi-dose vaccine vials.
Mercury itself is indeed toxic, with the compound methyl-mercury being responsible for Minamata disease, and toxic bio-accumulation in food chains (humans do consume low levels of mercury through natural sources such as seafood). However, thiomersal contains ethyl-mercury. Ethyl-mercury is not only a completely different compound to methyl-mercury but has also been shown to not accumulate in infants following vaccination.
If the studies confirming the safety of thiomersal in vaccines wasn’t enough, thiomersal has been removed from vaccines in the US, UK and EU. The UK has not used thiomersal since 2005 – one exception being the Pandemrix vaccine used in the swine flu (H1N1) pandemic. The presence of mercury in vaccines should therefore no longer be a valid cause for concern in the setting of modern vaccinology.
Another metal frequently cited as a worry for vaccine administration is aluminium. Again, not found as the raw element but rather as safe-to-use compounds, ‘salts’. Aluminium salts, such as aluminium hydroxide and potassium aluminium sulphate, are used as ‘adjuvants’. Adjuvants are components added to vaccines in an attempt to boost the immune response via several approaches and form a more robust long-term immunity. This enhanced immune response has a protective aspect, requiring less antigen content in the vaccine.
Humans naturally consume 30-50mg aluminium daily, found readily as a food additive in antacids, mineral water and breast milk. Conversely, vaccines contain less than 2 milligrams of aluminium salts – and therefore even less aluminium itself. In the UK, the largest dose of aluminium salts (1.5mg) is administered through the PVC, 6-in-1, and MenB vaccines. A recently published study found that aluminium levels in the blood and hair of infants did not correlate with immunisation, and there was no sign of dangerous bioaccumulation harmful to health.
Preserving me from the inside out?
On many vaccine ingredients lists, there may be a rather mysterious section labelled ‘excipients’ – this refers to the substances used in the production of vaccines which often are not added to the final product. One such substance is formaldehyde. Famous for its use in body embalming, one would immediately refrain from this being injected directly into your person. In vaccine production, however, formaldehyde is used to help inactivate pathogen toxins. Such techniques are used in the 6-in-1 vaccine, HepB vaccine, and various childhood boosters.
Importantly, formaldehyde is yet another compound which naturally occurs in the human body– including metabolic processes such as amino acid synthesis. A typical human infant possesses approximately 1.1mg of formaldehyde in their body – this is 10× greater than levels found in vaccines, which never exceed 0.1mg. For comparison, a pear contains approximately 50× more formaldehyde than what is a found in a vaccine injection – so consider this next time you’re getting your five-a-day.
Jelly in my vaccine?
For some religious communities, the use of animal products in the production of vaccines has caused confusion and a reduction of vaccine uptake. Porcine gelatin (from pigs) is used as a stabilising agent for some live vaccines. Distinct from the gelatine found in jelly, vaccine gelatine is highly purified, and broken down into peptides. Members of faith communities have shown differing views on the use of vaccines containing this component. Furthermore, a very small proportion of individuals receiving such vaccines do show some allergic side effects to the gelatine (~ 1 case per 2 million doses) – and so those with known gelatine allergies are encouraged to seek medical help before receiving a vaccine.
Helpfully, there are gelatine-free alternatives of many conventional vaccines, such as Priorix (the alternative to the classic MMRVaxPro) and Varilrix -the alternative to the Varivax chickenpox vaccine used in the UK.
Whilst the use of gelatine in vaccines is largely unproblematic, the use of this macromolecule should be considered for those with religious beliefs, or indeed those with known sensitivities to gelatine.
So, should I worry?
Vaccines may possess a lengthy and complex a list of ingredients which can be perceived as concerning on first look. However, it is important to know that each component has a carefully considered and researched position in the manufacturing process of each vaccine, and are not added without considering your safety. There are many more constituents of vaccines which are not discussed here but extensively investigated on other well-researched articles.
Perhaps instead of worrying about the contents of our life-saving vaccines, we should instead investigate the chemical make-up of ‘tangy cheese flavourings’ on a pack of Doritos before we next tuck in.