April 29 (Bloomberg) -- Sanofi-Aventis SA won’t be able to make shots against seasonal influenza, which kills as many as 500,000 people a year, should it be asked to develop a swine flu vaccine, Chief Executive Officer Chris Viehbacher said.

Swine flu, if it turns out to be less severe than its seasonal cousin, could deprive millions of people of a vaccine they need each year because drugmakers like Sanofi, the world’s biggest vaccine maker, and GlaxoSmithKline Plc don’t have the capacity to produce shots against several flus at the same time.

“That will be a very difficult choice,” Viehbacher said at a news conference today after the French drugmaker reported a 16 percent increase in first-quarter profit. “Clearly, if you make a swine flu vaccine and the pandemic doesn’t actually occur, we could end up with no seasonal flu vaccine.”

The number of worldwide cases of the virus reached by laboratory tests reached 112 today, the World Health Organization said. On April 27, the United Nations agency raised its global pandemic alert one notch to level 4, saying the disease is no longer containable. The level “does not necessarily mean that a pandemic is a foregone conclusion,” according to the agency’s guidelines. There are two higher levels on the WHO’s scale.

A pandemic could also be mild and cause fewer deaths than seasonal flu, said Ian Barr, deputy director of the WHO Collaborating Center for Influenza in Melbourne.

Coughs and Sneezes

“The decision to switch over is a tricky one,” said Martin Meltzer, an economist from the U.S. Centers for Disease Control and Prevention, in an interview yesterday. “If this isn’t the pandemic, you worry about the next flu season. If we have nothing because we switched to swine flu, that’s not good.”

At a time when scientists can tailor drugs to match a patient’s genetic profile and people live longer than ever, the flu, first described by Hippocrates 2,400 years ago, still has the power to make millions bed-bound for a week and kill the very young, the elderly and those weakened by chronic disease.

The virus travels in the fine spray of the coughs and sneezes of infected people. The three main seasonal flu strains -- H3N2, H1N1 and type-B -- cause 250,000 to 500,000 deaths a year globally, according to the WHO.

‘Big Decision’

It’s up to the WHO to tell vaccine makers including Sanofi, Glaxo, Wyeth, Merck & Co., Novartis AG and Baxter International Inc. which vaccine to make, seasonal or pandemic.

“It’s a very big decision,” WHO spokesman Gregory Hartl said at a press conference in Geneva yesterday. “It means no one in the next flu season will get their seasonal flu shots. We need to weigh the pros and cons.”

Viehbacher today said Paris-based Sanofi, which estimates it’s the world’s biggest maker of flu shots with 40 percent of the market, has asked employees to avoid traveling to and from Mexico. The drugmaker’s 3,000 local workers have been given face masks and transportation to the workplace to avoid exposure to the virus through public transport, Viehbacher said.

On the vaccine, “we have given our full commitment to health-care authorities that we’ll do whatever is necessary to help fight a pandemic if it should occur,” he said. “Health authorities are looking at which strain should go into the vaccine. We will cooperate fully.”

It would probably take about four months to get a vaccine ready, said Pascal Barollier, a spokesman for Sanofi’s vaccine unit in Lyon, in a telephone interview on April 27.

Sanofi Earnings

Sanofi said the dollar’s rise against the euro, demand for its Lantus diabetes medicine and cost cuts helped lift first- quarter adjusted net income to 2.18 billion euros ($2.89 billion), or 1.67 euros a share, in the first quarter, beating analysts’ estimates.

France’s largest drugmaker also said today it dropped 14 of 65 research projects, including experimental medicines for sleep apnea and depression, to focus on its most promising candidates. The company also plans to “accelerate” R&D partnerships and alliances as it needs to reinforce its pipeline, Marc Cluzel, who heads Sanofi’s R&D, said during a conference call today.

The stock rose 1.77 euros, or 4.3 percent, to 43.40 euros in Paris trading today, the biggest gain in two months.

To contact the reporter on this story: Albertina Torsoli in Paris at atorsoli@bloomberg.net

Last Updated: April 29, 2009 11:58 EDT