UPDATE 1-Pregnant women should get flu shot as winter bites-WHO

* Pregnant women, others at high risk should be vaccinated

* WHO concerned that some shying away from pandemic vaccine

* Ukraine outbreak kills 70, shows how can strike in region (adds WHO statement on Ukraine, new paras 6-8)

By Stephanie Nebehay

GENEVA, Nov 3 (Reuters) - Pregnant women and other people at high risk should be vaccinated against the H1N1 swine flu virus as the cold weather begins to bite in the northern hemisphere, the World Health Organisation (WHO) said on Tuesday.

It voiced concern that some vulnerable people are shying away from the pandemic vaccine, which the WHO stressed had not caused any unusual side effects in hundreds of thousands of people to have received it worldwide so far.

"Certainly the fact that the vaccine isn't being used by those who would have access to it and who would be in priority risk groups is of concern, yes," WHO spokesman Gregory Hartl told a news briefing.

At least 5,712 people have died from the swine flu virus, according to the United Nations agency. Health workers, pregnant women and people with conditions such as asthma are deemed at greatest risk and should be top priority for getting the shot.

"We have seen many, many instances of people in high risk groups such as pregnant women who have very severe disease or outcomes. These outcomes could be in all likelihood avoided if one were to get vaccinated," Hartl said.

A flu epidemic in Ukraine -- with more than 250,000 cases and 70 deaths from acute respiratory illness reported so far by national authorities on Tuesday -- may be an "early warning signal" as winter sets in, the WHO said.

"The outbreak in Ukraine may be indicative of how the virus can behave in the northern hemisphere during the winter season, particularly in health care settings typically found in Eastern Europe," the WHO said in a statement.

The former Soviet republic closed schools, banned public meetings and restricted travel last Friday for three weeks.

HITTING THE YOUNG

Unlike seasonal flu, which is most dangerous to the elderly, H1N1 is hitting younger adults and children especially hard.

The WHO recommends a single vaccine dose for protecting adults against H1N1. It has also urged governments to consider giving a single dose to as many children under age 10 as possible, but says more research is needed into child dosages.