GENEVA (AFP/Reuters) - The swine flu pandemic has grown unstoppable and all nations will need access to vaccines, a WHO official said Monday, as seven new deaths were reported and a study raised fresh concerns. Britain, Thailand and the Philippines all reported deaths on Monday, while Saudi Arabia shut an international school after 20 students were diagnosed with the A(H1N1) virus. As the death toll increased, the World Health Organisation official said a swine flu vaccine should be available as early as September and all countries would need to be able to protect themselves. A group of vaccination experts concluded after a recent meeting that the H1N1 pandemic is unstoppable and therefore all countries would need to have access to vaccines, said Marie-Paul Kieny, WHO director on vaccine research. Health workers should be at the top of the list for vaccination since they will be in high demand as people continue to fall sick, she added. Countries would be free to decide on their national priorities, but other groups should include pregnant women and anyone over six months old who has chronic health problems, the WHO official said. Particular attention would have to be paid to children since they are considered amplifiers of the spread of the virus, especially when gathered in schools, Kieny added. More than 90,000 swine flu cases have been reported worldwide, including 429 deaths, the most recent WHO numbers from last week show. While most cases have been considered mild, a study released on Monday said the virus causes more lung damage than ordinary seasonal flu strains but still responds to antiviral drugs. Virologists tested samples of the virus taken from patients in the United States as well as several seasonal flu viruses on mice, ferrets, macaque monkeys and specially-bred miniature pigs. They found that A(H1N1) caused more severe lung lesions among mice, ferrets and macaques than the seasonal flu viruses. But it did not cause any symptoms among the mini-pigs, which could explain why there has been no evidence that pigs in Mexico fell sick with the disease before the outbreak began among humans. The team also found that the virus was highly sensitive to two approved and two experimental antiviral drugs, including Tamiflu, now being hurriedly stockpiled around the world. This confirms the drugs role as a first line of defence against the flu pandemic, they said. The worry about the present strain of A(H1N1) is that it could pick up genes from other flu strains that would enable it to be both highly virulent and contagious, and these warnings are spelt out in the new study. Sustained person-to-person transmission might result in the emergence of more pathogenic variants, as observed in the 1918 pandemic virus, it says. Another concern is that the virus could acquire mutations enabling it to be resistant to Tamiflu. Collectively, our findings are a reminder that (strains of swine flu) have not yet garnered a place in history, but may still do so. Most of the deaths reported on Monday were in Asia, with Thailand reporting three fatalities and the Philippines two. Thailands death toll has now reached 21, while the Philippines has three deaths. Health officials in Britain announced the deaths from swine flu of a six-year-old girl and a doctor, bringing the number of fatalities there linked to the virus to 17. Nearly 10,000 Britons have been confirmed with swine flu but hundreds of thousands more are thought to have it. The school closure in Riyadh came with officials there especially concerned over swine flu with upwards of two million people expected to arrive over the next five months on pilgrimages to the Muslim holy cities of Mecca and Medina. Meanwhile, a family doctor and a six-year-old girl have died after catching H1N1 flu, health officials said on Monday, days after the first British death from the infection in an otherwise healthy patient. It means 17 people have now died in Britain after contracting the infection. Dr Michael Day, from Bedfordshire, north of London, died on Saturday at Luton and Dunstable Hospital, local NHS officials said. Tests showed he had tested positive for the H1N1 virus, known as swine flu, although the exact cause of death was still unknown. This news has come as such a shock to us all and we are completely devastated, said Dr Paul Hassan, senior partner at Priory Gardens Health Centre. I know the news will also come as a great shock to our patients, many of whom have known him for many years. Meanwhile Chloe Buckley, 6, from northwest London, died on July 9 at St Marys Hospital in London, NHS officials said. A post mortem will be carried out to see if she was suffering any underlying health conditions. We would like to extend our deepest sympathies to the family at this difficult time as they come to terms with their loss, said Simon Tanner, Regional Director of Public Health. On Friday, the government announced that a patient from Essex, eastern England, had died from the virus, but unlike all the others had no underlying health conditions. The Department of Health said last week the rapid spread of infection in London and the West Midlands was close to epidemic level. It said Britain had 9,718 laboratory-confirmed cases, the third most in the world behind the United States and Mexico, although the actual number of cases was likely to be higher. A total of 17 patients who contracted the virus, known as swine flu, have now died, including six in London. Until last week, all had underlying health issues and it is not clear in how many cases the patients had died as a direct result of the virus. Britains Health Minister Andy Burnham has said the government is projecting more than 100,000 new cases a day of the flu by the end of August. Most people who have caught the infection have suffered mild symptoms. The World Health Organisation declared on June 11 the outbreak of the virus was a pandemic and more than 94,500 cases have been reported worldwide.