Following the death of four men who had been inoculated against flu, Israeli authorities have suspended nationwide flu vaccinations.
Israeli Health Minister Yacov Ben Yizri says epidemiologists and public health experts are conducting an investigation and have also requested that the manufacturers French firm Sanofi-Aventis conduct its own investigation; meanwhile the vaccination programme has been suspended.
According to the hospital all the men were aged 52 to 76 and had suffered from serious conditions such as diabetes and heart disease and died between one and five days after they received their shots.
Three of the men, all residents of Kiryat Gat, were vaccinated at the same Kupat Holim Leumit clinic in their city and injected from the same vaccine pool.
All three had received flu shots in previous years with no unusual symptoms.
The cause of death of the fourth, a 67-year-old resident of Petah Tikva who was vaccinated at a Kupat Holim Meuhedet clinic, is at present unknown.
Officials hope an autopsy will determine the cause of his death.
Experts believe people aged 65 or older or those with severe heart conditions are at high risk from complications from influenza, and they encourage them to be vaccinated against it.
Influenza kills hundreds of thousands of people worldwide each year, and more than 140,000 Israelis, all at high or very high risk of complications from the flu, have been vaccinated for the flu virus in Israel this year.
Flu vaccines contain an inactivated virus, but the the risk of death from such vaccines is small.
Over 330 million people around the world each year receive flu shots supplied by the Pasteur Institute in France and the Chiron company in North America.