Vaccines against preventable illnesses like measles, tetanus, mumps and rubella are safe and effective, but healthcare professionals still find themselves having to push back against vocal anti-vaccination campaigns.
Parents looking for answers on the safety of vaccinations are led astray by fake news, hoaxes, as well as religious and cultural beliefs, and sometimes even threats of violence - which mean diseases once thought eradicated are making a comeback.
The problem facing medicine is global, where disinformation about vaccines is readily accepted as having equal or greater value than the work of scientists who have spent their careers fighting disease.
While immunisation has long proved to be one of public health's most cost-effective interventions, different countries and regions have their own issues, which makes the fight against diseases more difficult.
Accounts promoting an anti-vaccination agenda enjoy large followings on social media, and often tug at the heartstrings of followers, even though they present no evidence for their unsubstantiated claims.
One account on Instagram is @doctor_kolatova with 359,000 followers, run by a homeopath and a mother.
In a posted titled "After-effects of vaccines", Ms Kolatova tells the story of a baby in Kazakhstan who died the day after receiving vaccines for measles, polio, rubella and other illnesses.
"On whose conscience will be the death of the child?" she asks.
"Doctors deny blame and called a very convenient diagnosis of 'Sudden Infant Death Syndrome'," she writes, claiming that the "aggressive vaccines upset the balance of the body, especially the immune system".
Ms Kolatova deploys the debunked argument that the risk of vaccinating a child is far higher than the risks of them catching diseases "which are not serious and can be cured… but Sudden Infant Death Syndrome cannot".
In young children, measles can lead to pneumonia, swelling of the brain, permanent injury, and death. Polio can cause paralysis and death.
The idea that vaccines rewrite DNA appears widespread, but these claims do not go unchallenged, with one person asking: "Are you even qualified, authors of this nonsense?"
The eastern European nation is said to be the most affected country in Europe in terms of preventable diseases.
More than 15,500 measles cases have been recorded this year - and more than 60 deaths - while a large Romanian diaspora across the Continent has been identified as a driver for outbreaks in other countries.
According to the Balkan regional news agency BIRN, the spread of measles in the country is a result of distrust in Romania's health services "due to poor facilities and mismanagement".
However, anti-vaccine campaigners also play their part, with one leaflet being distributed in Bucharest playing on religious beliefs, saying "the measles vaccine contains the cells of aborted foetuses". The same leaflet also claims that unvaccinated children are healthier.
Prominent TV presenter Olivia Steer pushes an anti-vaccine agenda on social media and television chat shows. She's also an advocate of the recent theory that suncreams are a scam, and cause Vitamin D deficiencies.
Neither claim is true.
In order to increase the vaccination rate, United Nations children's agency Unicef and the Romanian health ministry have been conducting a door-to-door campaign in some regions, hoping to fully explain the benefits of vaccinations and the dangers of listening to conspiracy theories.
Poverty and security issues mean there has been a gap in vaccination coverage in Nigeria.
The World Health Organization (WHO) says that some 3.3 million unvaccinated children are at risk from measles, while polio cases have also been reported.
The Nigeria Guardian newspaper notes that poverty and a lack of health infrastructure are the greatest drivers in the spread of disease. "The major reason for having high numbers of unvaccinated children is due to poor logistics and funding," it says.
However, terrorism also plays its part in the continuing spread of otherwise preventable diseases.
The discovery of cases of polio in areas reclaimed by government forces from Islamist militant group Boko Haram is seen as a result of the group's complete isolation of the areas it controls from the rest of the country.
While Boko Haram is opposed to vaccines, echoing militant groups in South Asia saying that immunisation is a "Western plot to sterilise Muslims", the cutting off of their territories from the rest of Nigeria played a greater role in the re-emergence of polio than ideological considerations.
As a result, people displaced by the conflict against Boko Haram, either through liberation or fleeing the militant group, pose a risk to others because of their close proximity to unvaccinated people in refugee camps and host communities.
"Unless there is a breakthrough to reach those areas in Borno State, the entire polio programme is at risk," the WHO says.
Democratic Republic of Congo
People in parts of DR Congo are finding themselves at risk from Ebola as they do not trust a Canadian-developed vaccine.
This is because they distrust police and troops sent to protect medical workers, and suspicion of a "sudden" vaccination programme against the disease when other health crises have been ignored.
The Red Cross confirmed in April that "the Ebola outbreak in the Democratic Republic of the Congo is worsening as trust in the response effort falters. Disease outbreaks begin and end in communities. We must place communities at the very centre of all we do".
However, health organisations face an uphill struggle, with a study published in The Lancet finding that "nearly half of respondents believed that Ebola didn't exist or was invented to destabilise the region or to make money. People with those beliefs were far less likely to seek Ebola treatment, and about one-third of all respondents were unwilling to take the Ebola vaccine".
The outbreak in the east of the country is particularly dangerous because of the porous borders with Uganda, Rwanda and South Sudan.
It's led Congolese Nobel Prize laureate Dennis Mukwege to encourage locals to ignore false narratives about the vaccine, and to convince them that the deadly disease actually exists.
"As a doctor, I tell you that Ebola is not a false epidemic. It is real and deserves our attention, as well as our very committed struggles to put an end to it. To refuse to consider this danger is to open the door to us being decimated in isolation", he said.
However, social media users continue to spread doubt that the emergency is real, with comments variously claiming Ebola was "planted in the country for big business" and that it is an "Illuminati plot" in which the WHO is playing a part.
According to the News Minutes website, although half of the world's vaccines are produced in India, the country is in danger of falling victim to anti-vaccine hoaxes, largely driven by religion and tradition.
In one case in 2017, a nurse was attacked at a vaccination drive for schoolchildren in south-western Malappuram region. "There is false propaganda against the vaccination drive. Certain people still hold on to superstitions. But we are trying to overcome the situation by enlightening people," Health Minister KK Shailaja said at the time.
However, these hoaxes can now travel faster and further via social media such as WhatsApp, which has some 300 million users in India.
In April, the Wall Street Journal reported: "Dozens of schools in Mumbai have refused to allow health officials to carry out vaccinations in recent months, largely because of rumours shared on Facebook Inc's popular messaging app [WhatsApp] about the supposed dangers."
Tamil Nadu's director of public health, Dr K Kolandaswamy, warned that it "costs nothing" to spread hoax messages on social media, and they "encourage misinformed mobs".
"I feel that many of these people do this for cheap popularity and nothing more. It's a type of cult behaviour," he said.