Take a look at a timeline graph of polio or measles cases over the past 100 years and you’ll notice a striking trend – right around the mid-20th century, the zig-zagging peaks representing the number of infected persons suddenly crash to zero, and the line from there on out is nearly flat. These moments on the graphs correlate with the introduction of vaccines targeting those particular diseases.
Vaccines are up there with the automobile and the computer on lists of the greatest inventions of all time. Developed at the end of the 18th century (the first vaccines were for smallpox), they have been some of the most important tools for improving public health and protecting against serious diseases. Despite the overwhelming evidence for their efficacy, vaccines are nonetheless the subject of controversy. “Anti-vaxx” sentiments, which have spread easily through contemporary social media, are as old as vaccines themselves – one of the earliest examples of an anti-vaccination movement was in Stockholm in the 1870s, where smallpox vaccination rates plummeted because of religious and political objections. Shortly after, a smallpox epidemic broke out, convincing Stockholm residents to vaccinate.
The lessons learned in Stockholm were soon forgotten. History abounds with examples of similar movements influencing anti-vaccination behaviors, only to result in outbreaks of preventable diseases. In the late 1990s, measles vaccination rates in the UK and Ireland dropped after controversial campaigns linking vaccines to autism. As students of the history of medicine could have predicted, Ireland then suffered an outbreak of measles from 1999 to 2000. More recently, the introduction of vaccines for COVID-19 was marked by political tensions as anti-vaccination claims spread rapidly online and on social media platforms. These claims had real effects, and a 2021 study in the journal Nature Human Behavior found that “exposure to online misinformation about COVID-19 vaccines declined vaccination intent significantly in both the U.S. and U.K.”
What are some of these claims? What is their origin, and do they have any merit? As we will see, there is overwhelming evidence that vaccines, including the most recent COVID-19 vaccines and boosters, are safe and effective. Vaccination against COVID will continue to be a primary public health priority as the pandemic enters its fourth year, and working against misinformation will also be critically important. In this spirit, below are four questions or claims about vaccines, followed by the scientific consensus on the issue.
ONE: Is there a link between vaccines and autism?
No, there is no link, causal or otherwise, between vaccines and autism. Vaccine ingredients do not cause autism, and vaccinating children will not cause them to develop autism. Scientists and vaccinologists have extensively investigated claims about there being a causal relationship between vaccines and autism and have found zero evidence to support the idea, which only emerged in 1998 after Andrew Wakefield, a doctor in the UK, published a now-discredited and fradulent study claiming a link. Wakefield was struck off after the fraud was uncovered.
TWO: Were COVID-19 vaccines even tested before they were released?
Yes, they were. The vaccine developers didn’t skip any testing steps, but for the sake of time they did conduct some of the steps on an overlapping schedule to gather data more quickly. The same process of phase one, phase two, and phase three clinical trials that are seen with other vaccines were used for the development of the COVID-19 vaccines, but given their time-sensitive nature they were performed more rapidly than usual.
THREE: Do vaccines have dangerous side-effects?
No, for the vast majority of people vaccines in use today have only mild side-effects, such as soreness at the site of injection or mild fever (signs the vaccine is working to stimulate the immune system). Vaccines (such as the COVID-19 vaccines) undergo clinical trials to assess safety, and the number of individuals reporting serious side-effects is extremely low (less than a percent).
FOUR: Are vaccines supposedly to prevent infection completely? Why are people still getting COVID or the flu even if they are vaccinated against these viruses?
Vaccines are not perfect. They are meant to protect against serious illness and death, but nothing works 100%. Nonetheless, the Pfizer and Moderna vaccines are both close to 95% effective at preventing symptomatic COVID-19 in people, and highly effective at reducing hospitalization and death if a person is infected.
Vaccine hesitancy and anti-vaccination beliefs are difficult problems to address and solve, but vaccines are too important a tool to ignore the problem and hope it goes away. As misinformation spreads uncontrollably on social media, we must keep in mind that false claims have real impacts on people’s lives and can even be dangerous or deadly. The trend lines on graphs of polio and measles cases could easily trend back up if we are not careful.
