Vaccine myths

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Unfortunately, there are many myths and false claims about vaccines. They are as old as vaccines themselves. These claims have been consistently and repeatedly disproved by scientific evidence. Here are some examples:

The diseases that vaccines claim to prevent were already declining before vaccination thanks to improvements in hygiene.

This statement is partly true. However, improvements in hygiene do not explain the dramatic decline in vaccine-preventable diseases, nor its correlation with vaccination coverage levels. Nor can it explain certain specific achievements due to vaccination, such as smallpox eradication and polio elimination.

The diseases that vaccines are intended to prevent are almost eradicated. This means there’s no need to get vaccinated.

This statement is partly true. They are rare diseases, but the micro-organisms that cause them still exist and circulate around the world. They can infect any unprotected person. It is important to remember the concepts of individual protection and herd immunity.

The immunisation produced by ‘natural’ disease is better than that produced by vaccines.

This statement is false. Vaccines provoke an immune response similar to that of natural infection, but at the same time prevent the disease and its complications, which can be very serious, from developing.

There have been outbreaks or epidemics in which most of the sick people who caught the disease were vaccinated.

This statement is an incorrect interpretation of the reality of the situation. In any outbreak or epidemic, there is always a proportion of vaccinated and unvaccinated people. There are many vaccinated people, and their risk of infection is low. There are few unvaccinated people, and their risk of infection is high. Data always requires analysis: what is the proportion of cases among the unvaccinated versus the vaccinated?

Children shouldn’t be vaccinated in their first year of life, because their immune system is immature.

This statement is false. The risk of infectious disease is highest in a child’s first years of life, with a higher risk of complicated disease and death. Delaying vaccination leaves children in a vulnerable situation.

Vaccines contain toxic mercury (thiomersal).

This statement is false. Practically no vaccine currently in use contains thiomersal. Thiomersal accounts for 0.1% of all human exposure to mercury. The mercury that is still used in some vaccines (ethylmercury) poses no risk to health. Toxic mercury is methylmercury, which is not a component of vaccines.

Vaccines contain toxic aluminium.

This statement is false. There has never been any evidence of harm or poisoning from aluminium linked to vaccination. There are many other much more significant and common natural sources of aluminium exposure.

Vaccines cause autism (ASD: autism spectrum disorders).

This statement is false. It has been overwhelmingly demonstrated that there is no link between autism and vaccines. The study (published in The Lancet in 1998) that suggested this possibility was shown to be a case of fraud. It was retracted and its author (Andrew Wakefield) was struck off the General Medical Council and is barred from practising medicine in the UK.

Vaccines cause diabetes, multiple sclerosis, inflammatory bowel disease and sudden infant death (SIDS).

This statement is false. No evidence for these associations has been demonstrated. Most of the time it is a case of a temporal relationship (coincidence), with no cause-effect relationship.

Substantiated information by:

Anna Vilella
Antoni Trilla
Marta Aldea

Published: 13 January 2022
Updated: 13 January 2022


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