I believe that knowledge of science can empower people to make better decisions for their health and lives. When it comes to vaccine, that decision could be a life or death one.
When I heard about the breaking news today, reporting that a six-year-old Spanish boy who had become infected with Corynebactuerium diphtheria earlier this last month, died of diphtheria, I could not believe this would happen in 2015. This is the first case of diphtheria in Spain in 29 years since widespread vaccinations have allowed successful eradication of the disease worldwide. The boy, however, was not vaccinated against diphtheria because his parents were against him getting inoculated amidst controversies over the shot’s potential side effects. In the small Spanish town of Olot 10 more people, of which 9 children, were exposed to the bacterium but did not develop the disease as they were all vaccinated.
In the last 10 years, the world has seen parents all over the world rejecting vaccination. Parents have attempted to find answers to aid their decision but getting information on vaccines from the internet can be a scary and confusing experience. I’d like to provide some answers to the more recurrent concerns the public faces when thinking about vaccines based on rigorously tested scientific and epidemiological evidence.
I hope this information can be useful to you and can help avoiding the re-occurrence of preventable diseases.
In the last five years, there has been a decrease in the number of parents vaccinating their children. So what?
About 800 people die a year as a result of parents not vaccinating their children. Basically, two people every day in the United States alone die of causes that could have been prevented by vaccinations 
What about the potential risk of deaths from vaccination?
Severe and extreme reactions to vaccination are extremely rare. As with any drug or medicine, there is a small chance that vaccines may cause an adverse reaction. Every year in the United States, millions of people are vaccinated for a wide range of diseases and fewer than 1% have non-life threatening allergic reactions to the vaccine. The rate of death or severe reactions to vaccines, for instance the MMR shot, is less than one in a million vaccinations4. The rate is so low, it is actually difficult to be certain the adverse reaction was directly linked to the vaccine. To put that in perspective, Tylenol poisoning kills more than 100 people every year.
What about the lives that vaccines save?
Vaccines save millions of lives worldwide every year. Perhaps the most impressive result of a vaccination can be seen with the smallpox vaccine. In the past, about 80% of children and half of the adults infected with the smallpox virus died of this devastating disease. Two million people died every year during the 1960s from smallpox. Aggressive vaccination campaigns led to the complete eradication of the disease – that’s right, nobody in the world is infected with smallpox these days! The last smallpox case was diagnosed in 1977. Thanks to this vaccination, the world went from 2 million deaths to zero in less than 10 years.
What about mercury, and other potentially toxic substances contained in vaccines?
Mercury hasn’t been used in vaccines since 2001. All routinely recommended childhood and adult vaccinations, and most influenza vaccines to date, do not contain mercury. While there may be other ingredients in vaccines, such as preservatives, stabilizers and enhancers, they are all FDA-approved7.
Vaccines can contain small amounts of formaldehyde and aluminium but the amount of these substances in vaccines is several hundred times lower than what we are routinely exposed to in our diet. This is the same for traces of mercury in some flu vaccines.
Mercury hasn’t been used in vaccines since 2001.
Do vaccines cause autism, ADHD, and other non-lethal disorders?
No link has been proven between autism and vaccines. Since the 1950s, mass vaccination of millions of infants and adults has been occurring, preventing thousands of deaths. The fraction of children affected by autism is currently 1 in 68 which means that just 1.7% of children suffer from autism. Right now, about 90% of children receive vaccinations. Just looking at the numbers, vaccines are unlikely to be the distinguishing factor that confers susceptibility to autism.
Why do people say there is a link between vaccines and autism?
The unfounded link emerged from a fraudulent scientific study that kick-started much of the largely unfounded mass hysteria about vaccines that we witness today. The study was retracted10 and the doctor responsible for the fraud was banned from any future research. By then, however, the damage had been done. After the fabricated study was reported, many labs attempted to find evidence for a link between vaccines and autism without success, which further discredits the original “research”. There have been hundreds of studies disproving the link, showing with great statistical significance and confidence, that there is no link between vaccines and autism.
I don’t like the fact that my newborn child has to get multiple vaccination shots. Is it harmful for the baby?
Newborns are tougher than you think! The amount of immune challenges young children fight daily is a thousand times greater than all life-time vaccination doses combined. Already at birth, the passage from the secure environment of the womb through the bacteria-filled vaginal canal is a shock to the baby’s immune system – a good shock! Caesarean birth has been associated with higher risk of allergies, asthma and inflammation later in life because the baby is not exposed to those immunity-inducing bacteria. Vaccines have a similar effect. Challenging the infant immune system with vaccines is a safe way to get it to work against preventable diseases. While we live in an environment that offers fewer challenges to the immune system (where we over-sterilize and don’t “let the babies play in mud anymore”), vaccinations are actually a great way to exercise the immune system and keep all its parts functioning properly.
Are vaccines makers just making money from vaccinations that are not actually for our own good?
Most vaccines are cheap for patients. The evidence for the benefit of vaccines is so overwhelming and the consequences of not vaccinating so catastrophic, that vaccines are made by many pharmaceutical companies and the process is cheap. 
You are saying, basically, that I should vaccinate my children. Yes?
Yes! Decades of scientific and medical research have made it possible for us to virtually eradicate diseases preventable by vaccinations. In the last century, childhood mortality in developed countries has decreased 99%, largely due to vaccines and antibiotics. Many charities, foundations and organizations promote important immunization campaigns for preventable diseases in developing countries. Why would the leading nations that have worked to advance science and human health through vaccine discovery want to stop taking advantage of that?
Shouldn’t we let parents be free to make their own choice about vaccination?
Disease protection derived from vaccines doesn’t work on individual choices, it must be a collective effort involving all the members of a society (especially, in the globalized world of today). Vaccination rates must stay high to keep a whole community protected from a certain disease, a concept called ‘herd immunity’. The rates required to continue preventing outbreaks and epidemics of certain diseases are variable, with 85% immunization rate needed to protect us from polio and 95% required to eradicate the highly contagious and deadly measles. The people with the highest risk from these diseases are young children, immune-compromised individuals – such as cancer patients – and the elderly. Our need for each individual to vaccinate is even greater to ensure that the whole community, even those with the highest risk, remains healthy. Vaccinations are not about individual choices, but about social responsibility and safety.
Fine, I see the benefits of vaccines but are all vaccines equally necessary? For instance, against seasonal flu?
Influenza is the 7th most deadly disease in the United States, right behind diabetes. Every year, 55,000 adults and children die from the flu and pulmonary complications derived by the flu, while severe adverse reactions to the flu shot are 0.00000001%, so why not vaccinate? Also, remember the concept of herd immunity discussed above. Not vaccinating against the flu means exposing more people to the virus for a prolonged period of time, including immune compromised individuals. An immunized person that comes in contact with the influenza virus clears the infection in 24 hours. A non-vaccinated person is infected and contagious for almost a week, often asymptomatically at first, which dramatically increases spreading of the disease. It is also important that the flu vaccine is taken yearly.
Asking questions about vaccines is expected, just like any other medication. However, be sure to take immunization advice from your doctor, immunologist, or a medical expert on vaccinations. Refrain from drawing conclusions based on assumptions, personal beliefs, or information from unreliable sources. After all, it’s a choice about life: yours, your kids and everyone that comes in contact with you in your lifetime. Make that be the right choice.
Dr. Simona Giunta, Ph.D.
President of Know Science
This blog was made possible by sharing the knowledge and information collected from several scientists and immunologists, and is based on real questions submitted by the Know Science audience. Special thanks to Professor Juan Lafaille, Kate Bredbenner, Danielle Sonnenberg and Alistair Field for critical reading and expert advice. We welcome any additional questions you may have via our Ask The Expert form and we encourage your comments below.
 Further reading on the Centre for Disease Control and Prevention website. What would happen if we stopped vaccinations? http://www.cdc.gov/vaccines/vac-gen/whatifstop.htm
 American Association of Poison Control Centers. Practice Guideline: Acetaminophen Poisoning: an Evidence-Based Consensus Guideline for Out-of-Hospital Management. Clinical Toxicology, 2006: Vol. 44; pp. 1–18.
Wolf SJ, Heard K, Sloan EP, Jagoda AS; American College of Emergency Physicians. Clinical policy: critical issues in the management of patients presenting to the emergency department with acetaminophen overdose. Ann Emerg Med. September 2007: Vol. 50; pp 292-313.
 Updated aluminum pharmacokinetics following infant exposures through diet and vaccination. Vaccine 29 (2011) 9538-9543 doi.org/10.1016/j.vaccine.2011.09.124