A major immunisation programme is underway in Pakistan to combat a large rise in the number of people with measles.
"This was a tragedy that was waiting to happen. We have been predicting for a while now that without adequate cover with routine immunisation in many parts of Pakistan, notably in rural populations, that there was bound to be a situation where you would have an outbreak like this .... So what we are seeing this year is an absolute reflection of dropping the ball in covering an adequate cohort of children in rural and poor populations of Pakistan, particularly in the south, against a completely preventable disorder like measles."
- Dr Zulfiqar Ahmed Bhutta, a child health expert
The immediate challenge is to vaccinate almost three million people in the worst affected areas. But it is an enormous task - and a dangerous one.
Aid workers involved in vaccinations are being threatened, attacked and even shot dead by armed groups who suspect the programmes are meant to harm them.
The latest figures from the World Health Organization (WHO) show the number of measles cases in Pakistan has increased from 4,000 in 2011 to 14,000 in 2012. Of those, 306 died last year - up from 64 deaths in 2011.
The worst hit area is the southern Sindh province where 210 children have died - almost half of them in December alone.
The United Nations Children's Fund (UNICEF), says measles is still a leading cause of death among young children.
It is a highly contagious virus, infecting the respiratory system, and passed on by coughing and sneezing and close personal contact.
But it can be prevented - vaccination programmes worldwide resulted in a 74 percent drop in measles deaths between 2000 and 2010.
In 2000, there were more than half a million deaths. Ten years on, that figures was down to 139,000.
However, in Pakistan, some people are suspicious of vaccination programmes.
The reason for their suspicion is that, in 2010, the CIA set up a phony vaccination drive against Hepatitis B to help track Osama bin Laden.
"What the government has done is basically they have committed a vaccination suicide themselves. The fact is that in Pakistan, there's a very strong perception which is backed by facts on [the] ground, that this vaccination campaign in Pakistan has been used by [the] CIA and foreign secret services for espionage and spying. When these facts were identified ... the rage and anger in the nation was palpable .... American CIA has committed the greatest disservice to humanity by using these humanitarian programmes for spying and espionage against the state of Pakistan."
- Zaid Hamid, a security analyst
A Pakistani doctor was recruited to carry out the work in poor villages. His goal was to gain entry to the compound where bin Laden was suspected of hiding and get DNA samples from those living there.
The programme apparently failed. And the doctor is now serving 33 years for treason.
Some groups say the vaccination programmes are used to sterilise Muslims, or cause them harm.
The Taliban has repeatedly threatened health workers involved in vaccination work. And in recent weeks, a number of health workers have been shot dead.
It is unclear who is behind the attacks.
Gunmen ambushed and shot dead six Pakistani women and a male doctor in northwest Pakistan on January 1. The victims worked for an aid agency involved in health education and vaccinating children against polio.
And just two weeks earlier, nine health workers involved in a similar programme were shot dead in a series of attacks in Peshawar and Karachi.
Pakistan's parliament passed a resolution denouncing the attacks in December.
Raja Pervez Ashraf, Pakistan's prime minister, said: "The polio workers were on their way to administer drops to our children to save them from polio. Should they have been riddled with bullets? Which society, which religion, gives permission for such savagery? I believe, Mr Speaker, that the resolution passed by this House is against those terrorists, against those enemies of humanity, and not against ordinary citizens. This is for the safety of the ordinary citizens, for safeguarding the lives of ordinary Pakistanis. We have passed this for the protection of our children, for getting them out of the clutches of those terrorists who want to send them to the valley of death."
On this episode of Inside Story, we discuss Pakistan's fight against measles and the reasons why some do not trust the vaccination programmes to fight the disease. Joining the conversation, with presenter Laura Kyle, are guests: Zaid Hamid, the head of Brasstacks, a security think tank, and Dr Zulfiqar Ahmed Bhutta, the head of the division of women and child health at Aga Khan University.