Vaccines have revolutionized medicine. Thanks to vaccines, a number of life-threatening diseases are now under control - and in some instances, the diseases have been eliminated altogether.
As a result, vaccines prevent 2 to 3 million deaths each year. But according to the World Health Organization there are still far too many children around the world who are not receiving immunizations.
To make sure children are being vaccinated, most countries have some sort of vaccination policy - although the details vary widely.
Some nations like to focus on education and leave the choice of vaccination up to the individual, while other countries offer financial incentives for vaccinating children.
Plus, a number of countries have gone even further. Below is a list of ten nations that have made vaccinations mandatory.
Slovenia has one of the most aggressive and comprehensive vaccination policies. In Slovenia, there are nine vaccinations that are mandatory, including hepatitis, measles, polio and pertussis.
To get out of these vaccinations, individuals can submit medical exemptions, but reasons of religion or conscience are not accepted. If an individual fails to receive their mandatory vaccinations, they are penalized with a fine.
And the strategy is clearly working. The nation has compliance rates of up to 95 percent for mandatory vaccines.
In Belgium, only the polio vaccine is mandatory. The law, which requires three doses of polio vaccine before 18 months, has been in place since 1966, despite multiple attempts to remove it.
Plus, the Belgian National Bureau for Childbirth and Childhood - governing French-speaking Belgium - requires vaccinations against polio, diphtheria and whooping cough (pertussis) in order to attend French-speaking nurseries or childcare centres.
Compared to other countries, Latvia has a mandatory vaccination policy that's a little different. In Latvia, vaccinations are only mandatory for state institutions and vaccination providers. Meanwhile, for the public it is simply "recommended."
But if an individual declines a vaccination, there is a process. The health care provider must explain the health consequences and then the individual must sign a document of refusal, acknowledging they have been informed of the risks.
4. United States
All of the states in the US require vaccination for school attendance. Most states allow medical, religious and philosophical exemptions, but in Mississippi, California and West Virginia the rules are a little stricter. These three states only allow for medical exemptions, not religious or philosophical exemptions.
"Thanks to the [Vaccines for Children] program, children in our country are no longer at significant risk from diseases that once killed thousands each year," said CDC Director Tom Frieden.
"Current outbreaks of measles in the US serve as a reminder that these diseases are only a plane ride away. Borders can't stop measles, but vaccination can."
Australia's vaccination policy called "No Jab, No Pay" is similar to the US. The policy only allows children who are up-to-date with their vaccinations to attend preschool and child care centers.
Plus, in Australia if a parent does not vaccinate their child, they do not receive the financial incentives for doing so, which includes a family tax rebate and $11,000 in child care benefits. Medical and religious exemptions are allowed, but conscientious objections are not.
Unfortunately, the debate surrounding vaccines and autism is still raging in Italy. In 2012, a court even awarded damages to a family who claimed their child's autism was caused by a vaccine. Three years later the decision was overturned, and the government has been quick to implement new vaccination policies.
Now, Italian parents must prove their child has received 12 specific vaccinations – including measles, rubella and chickenpox - before their child can attend a government-funded nursery or preschool.
The policy does allow medical exemptions for certain children, but conscientious objections from parents are not allowed. Plus, if parents refuse to comply, they receive a hefty fine.
This year, Germany tightened their vaccination laws because of a measles outbreak. Now, German parents must submit proof of vaccination counseling for their kids to their kindergartens. If they do not, the schools are forced to notify the German health authority and their children could be expelled.
Unlike Italy, in Germany it is not considered an offence to refuse vaccination.
The rates of vaccination are scarily low in Romania. The ministry in Romania has confirmed that 224,202 children aged 9 months to 9 years have yet to be vaccinated against measles.
This year, after a measles outbreak took 32 lives in Romania - the most in Europe - the government announced they would be introducing a mandatory vaccination policy.
The health minister even went so far as to fire the county managers in areas with low vaccination rates, and a draft of the new law is being discussed by the government.
Vaccines are deeply misunderstood in France. A recent survey found more than three out of 10 French people don't trust vaccines, and only 52 percent said the benefits of vaccination outweigh the risks. As a result, France is the latest European country to make vaccination mandatory.
As of 2018, parents will be legally obliged to vaccinate their children. Right now, only three diseases are mandatory in France: diphtheria, tetanus and polio. The new policy would make all the vaccines which are recommended by health authorities compulsory - 11 in total.
Canada's vaccination rates are impressive. About 85 percent of children in Canada are completely vaccination, and less than 2 percent of parents are strongly opposed to vaccination. Nevertheless, there is no mandatory vaccination policy for all of Canada. Instead, the vaccination policies differ from province to province.
Right now, there are just three provinces that have mandatory vaccination policies, but they only apply to children about to enrol in school. Ontario and New Brunswick require immunization for diphtheria, tetanus, polio, measles, mumps, and rubella immunization. Meanwhile, Manitoba requires only a measles vaccination.
In each case, parents are allowed to apply for medical and religious exemptions, and even exemptions out of conscience.