Dr. John Simon said that even if a vaccine is developed, there is a possibility that the strain of coronavirus that causes SARS could mutate by then.
"Vaccines normally take five years to develop. Vaccines have to go through several types of trials. They have to go through an efficacy trial to make sure they work. They then have to go through a safety trial to make sure they don’t kill you," said Simon, who has written a number of research papers on SARS.
He added, "I could not really see a very effective vaccine coming out for at least one year or possibly two years. Even if the virus comes out, what if the virus mutates? We might need another vaccine. We might need a different vaccine every year. This is possible."
The first vaccine that could feasibly be made would be a killed vaccine, wherein the virus is killed and a vaccine made out it. When injected, the body manufactures antibodies that can recognize the live virus. This type of vaccine may be available within a year.
"However, they are not that effective. The live attenuated vaccine (composed of the weakened virus) would be highly effective, but would probably take at least two years, even (if fasttracked) in every laboratory in the world," Simon said.
Simon, who is in Manila to conduct a series of lectures, said it would be very difficult for a person to be infected with SARS due to precautionary measures taken inside the airport.
"If you have a SARS case in the airplane, how many people would have SARS in that airplane? The answer is that very few cases have actually been that way. And indeed, the cases which have been spread appeared to have been spread only through close contact with the person who has been sitting in that airplane," he said.
Simon said that with very few people traveling by plane due to the scare generated by the SARS outbreaks, travelers are not at much risk.
"Consider all the hundreds and thousands of people who have been flying in the last month, only a few people have gone down with SARS. From an aviation point of view, it is not a big deal. The danger of flying is that you have an index case incubating the disease, who comes into the country and affects many, many people," he said.
Now, travelers could have a couple of rows between themselves and the next passenger, which minimizes the chances of contracting SARS compared to a month ago, Simon said.
Earlier, a Hong Kong expert told Sunday’s La Repubblica daily that developing an effective vaccine for the killer disease will be extremely difficult because the virus keeps mutating into new forms.
Arthur Van Langerberg, a virologist at Canossa hospital in Hong Kong, one of the cities worst hit by the outbreak, said that even if researchers found a vaccine in the next six months it was unlikely to be effective since the virus would have mutated in the meantime.
"We must be aware that we’re going to have trouble getting rid of SARS," the Italian paper quoted him as saying.
SARS, which scientists have confirmed to be a mutant form of the coronavirus – the cause of the common cold – has claimed more than 200 lives so far and infected a further 4,500 people worldwide, mostly in China and Hong Kong.
"Because coronaviruses are so adaptable, it will be difficult to develop an effective vaccine for this disease," La Repubblica quoted him as saying.
Van Langerberg said that there was a very real risk of SARS spreading across Europe next winter – the season when people most frequently suffer from common colds – and called on Europe to be vigilant.
He also said that as a physician he was afraid of SARS because it was highly contagious.