There may be no vaccine yet to protect against the spreading swine flu, but in a season when ordinary influenza is also threatening to encroach on summer, health experts say it’s still not too late to get a flu shot — if you can find one.

People who put off flu vaccinations earlier in the season, particularly those in high-risk groups, still may be able to protect themselves from the worst effects of the seasonal virus that’s lingering longer than normal, said Dr. William Schaffner, chairman of the department of preventive medicine at Vanderbilt University and a spokesman for the Infectious Disease Society of America.

“There’s still some time to do it and there still will be some seasonal flu perking along,” Schaffner said. “I would say, by all means, get vaccinated.”

That’s more a recommendation than a formal public health strategy. Even as health officials in the United States grapple with the novel H1N1 swine flu virus that has sickened more than 5,000 people in this country, hospitalized more than 200 and contributed to at least seven deaths, they worry that levels of regular flu remain high for this time of year.

“There’s still a lot of seasonal influenza going on,” said Dr. Tony Marfin, the epidemiologist for communicable disease in Washington state, part of the Northwest region where levels remain elevated.

Higher than usual levels of flu also are being detected in the Southeast and the Southwest, according to the federal Centers for Disease Control and Prevention.

CDC officials have been discussing the prospect of a summer flu season, but there are no plans to call for large-scale extended vaccinations, said spokesman Tom Skinner.

That’s mostly because the CDC and other experts aren’t exactly sure how many of the 146 million doses of seasonal vaccine manufactured this year they still can count on, Schaffner.

“There is a limited amount of that vaccine left over, but no one is sure where it is,” Schaffner said. Until the end of the season, when providers return unused doses, it's not clear how much vaccine remains with manufacturers and how much remains in doctors' offices and clinics.

U.S. flu vaccines expire June 30

Another twist is that all of the seasonal vaccine produced for the United States this year expires on June 30, so people suddenly inspired to get regular flu shots need to hurry. Retailers such as Walgreens, which provides more than 1 million drugstore flu shots each winter, say they stopped stocking clinics at the end of March.

But flu vaccine suppliers and distributors said this week that they still have ample supplies and some public health departments and private doctors said that patients seeking flu shots simply have to ask.

“There is definitely availability,” said Bryan Goodin, adult immunization coordinator for the Oregon Public Health Division, who estimates that at least several thousand doses of vaccine remain available in his state. In California, public health officials said tens of thousands of doses are left.

Workplace health programs also may have easy access if employees want late-season flu shots, said Andrew Shulman, chief operating officer of Affiliated Physicians, a New York firm that provides health services, including flu shots, for some 800 companies.

“We have a roster of over 200 nurses who would be happy to help,” he said.

Private insurers and Medicare should cover the costs of the shots, if the benefit hasn't already been used. Typically, flu shots cost between $7 and $25, depending on where you get them.

Last year, 141 million doses of influenza vaccine were produced nationwide and only 112 million doses were used, according to industry figures. Most of the unused flu vaccine is either returned for credit or discarded as medical waste, experts said.

In typical years, influenza winds down by late May and early June, but this year, surveillance systems are detecting higher levels than normal of flu-like illnesses, said Dr. Anne Schuchat, a public health director with the CDC.

Nationally, about 2.6-percent of visits to outpatient clinics in a surveillance system were for people reporting flu-like illness during the week ending May 9, according to latest CDC figures.

CDC officials get concerned when flu reports top the national baseline of 2.4 percent of visits. This late in the spring, flu-related visits typically dip to less than 1-percent. 

Part of the bump in flu visits obviously is caused by the increased awareness and monitoring of the outbreak of the novel swine flu virus, which now accounts for 78-percent of new flu cases. But Schuchat said recently that flu-like illness visits increased even when attention to the new strain abated for several days. Officials said it remains a bit of a mystery why seasonal flu is up even as swine virus continues to spread.

Although experts predict that both swine flu and regular flu will level off with warmer temperatures and higher humidity in the Northern Hemisphere, that’s by no means certain.

CDC officials have long recommended that visitors get vaccinated against seasonal flu before traveling to the Southern Hemisphere from April through September, when flu season there is at its peak.

Seasonal vaccine doesn't protect against swine flu

Health experts emphasized that the seasonal vaccine does not provide protection against the new swine flu strain. Global health officials are still pondering whether and how to begin producing a vaccine that would target the novel H1N1 virus. On Tuesday, the World Health Organization reported that the swine virus was having a difficult time growing in laboratory settings and that production of a vaccine might not begin until mid-July at earliest, weeks later than originally hoped.

But in a country where the CDC estimates that regular flu sickens millions of people each year, leading to more than 200,000 hospitalizations and contributing to 36,000 deaths, seasonal vaccinations remain an important protection. Only about 20-percent to 30-percent of eligible people get appropriate flu vaccines, CDC experts say.

People recommended to have flu vaccinations include children aged 6 months to 18 years, people older than 50, pregnant women, health care workers and people with underlying health conditions such as asthma, heart disease, kidney disease and blood or metabolic disorders, including diabetes.

“It is a serious illness,” Marfin said.

Summer colds are a cruel oxymoron

Runny noses and hacking coughs are especially vile when it's sunny outside.

In a typical year, “cold season goes pretty much through the school year and flu season is narrower, usually falling between December and March,” says Dr. Neil Schachter, medical director of the respiratory care department at Mount Sinai Medical Center in New York and author of “The Good Doctor’s Guide to Colds and Flu.” “This is a very unusual season.”

Generally, the U.S. suffers through 1 billion to 2 billion colds annually with the average adult coming down with about two a year (kids have three to four times that amount). Summer colds, while more annoying, are less common since we tend to be outdoors more (as opposed to huddling inside coughing and sneezing all over each other) and because the sun’s ultraviolet rays kill cold viruses, which can live on surfaces for up to 24 hours.

Unfortunately, some of the 200 or so viruses that cause common colds are still able to survive and infect us — usually just in time to ruin a long-awaited vacation.