Questions and answers on immunization and vaccine safety
Vaccines are necessary — and good hygiene, sanitation, clean water, and nutrition are insufficient for stopping infectious diseases. If we don’t maintain optimum rates of immunization or “herd immunity”, the diseases prevented by vaccination will return. While better hygiene, sanitation and clean water help protect people from infectious diseases, many infections can spread regardless of how clean we are. If people are not vaccinated, diseases that have become uncommon such as pertussis (whooping cough), polio and measles, will quickly reappear.
2. Are vaccines safe?
Vaccines are safe. Any licensed vaccine is rigorously tested across multiple phases of trials before it is approved for use, and regularly reassessed once it is on the market. Scientists are also constantly monitoring information from several sources for any sign that a vaccine may cause an adverse event. Most vaccine reactions are usually minor and temporary, such as a sore arm or mild fever. In the rare event a serious side effect is reported, it is immediately investigated.
It is far more likely to be seriously injured by a vaccine-preventable disease than by a vaccine. For example, in the case of polio, the disease can cause paralysis, measles can cause encephalitis and blindness, and some vaccine-preventable diseases can even result in death. While any serious injury or death caused by vaccines is one too many, the benefits of vaccination greatly outweigh the risks, and many more illness and deaths would occur without vaccines.
3. Do vaccines provide better immunity than natural infections?
Vaccines interact with the immune system to produce an immune response similar to that produced by the natural infection, but they do not cause the disease or put the immunized person at risk of its potential complications. In contrast, the price paid for getting immunity through natural infection might be cognitive impairments from Haemophilus influenzae type b (Hib), birth defects from rubella, liver cancer from hepatitis B virus, or death from complication due to measles.
4. Do I need to be vaccinated against diseases that I do not see in my community or my country?
Although vaccine-preventable diseases have become uncommon in many countries, the infectious agents that cause them continue to circulate in some parts of the world. In a highly inter-connected world, they can cross geographical borders and infect anyone who is not protected.
Two key reasons to get vaccinated are to protect ourselves and to protect those around us. Successful vaccination programmes depend on the cooperation of every individual to ensure the wellbeing of all. We should not rely on people around us to stop the spread of disease; we, too, must do what we can.
5. Can a child be given more than one vaccine at a time?
Scientific evidence shows that giving several vaccines at the same time has no negative effect on a child’s immune system. Children are exposed to several hundred foreign substances that trigger an immune response every day. The simple act of eating food introduces new antigens into the body, and numerous bacteria live in the mouth and nose. A child is exposed to far more antigens from a common cold or sore throat than they are from vaccines.
The key advantage of having several vaccines at once is fewer clinic visits, which saves time and money. Also, when a combined vaccination is possible (e.g. for diphtheria, pertussis and tetanus), that will result in fewer injections and reduces discomfort for the child. A number of steps can also be taken to reduce pain at the time of vaccination.
6. Do I need to be protected against influenza through vaccination?
Influenza is a serious disease that kills between 300 000 to 500 000 people worldwide every year. Pregnant women, small children, elderly people with poor health and anyone with a chronic condition, like asthma or heart disease, are at higher risk for severe infection and death. Vaccinating pregnant women has the added benefit of protecting their newborns (there is currently no vaccine for babies under 6 months).
Seasonal influenza vaccines offer immunity to the 3 most prevalent strains circulating in any given season. It is the best way to reduce your chances of severe flu and of spreading it to others and have been used for more than 60 years. Avoiding the flu means avoiding extra medical care costs and lost income from missing days of work or school.
7. What preservatives are used in vaccines?
Thiomersal is an organic, mercury-containing compound added to some vaccines as a preservative. It is safe and the most widely-used preservative for vaccines that are provided in multi-dose vaccine vials. There is no evidence to suggest that the amount of thiomersal used in vaccines poses a health risk.
8. What about vaccines and autism?
The 1998 study which raised concerns about a possible link between measles-mumps-rubella (MMR) vaccine and autism was later found to be seriously flawed and fraudulent. The paper was subsequently retracted by the journal that published it. Unfortunately, its publication set off a panic that led to dropping immunization rates, and subsequent outbreaks of these diseases. There is no evidence of a link between MMR vaccine and autism or autistic disorders.