By MIKE STOBBE
Associated Press

Researchers have discovered the first U.S. cases of whooping cough caused by a germ that may be resistant to the vaccine.

Health officials are looking into whether cases like the dozen found in Philadelphia might be one reason the nation just had its worst year for whooping cough in six decades. The new bug was previously reported in Japan, France and Finland.

"It's quite intriguing. It's the first time we've seen this here," said Dr. Tom Clark of the Centers for Disease Control and Prevention.

The U.S. cases are detailed in a brief report from the CDC and other researchers in Thursday's New England Journal of Medicine.

Whooping cough is a highly contagious disease that can strike people of any age but is most dangerous to children. It was once common, but cases in the U.S. dropped after a vaccine was introduced in the 1940s.

An increase in illnesses in recent years has been partially blamed on a version of the vaccine used since the 1990s, which doesn't last as long. Last year, the CDC received reports of 41,880 cases, according to a preliminary count. That included 18 deaths.

The new study suggests that the new whooping cough strain may be why more people have been getting sick. Experts don't think it's more deadly, but the shots may not work as well against it.

In a small, soon-to-be published study, French researchers found the vaccine seemed to lower the risk of severe disease from the new strain in infants. But it didn't prevent illness completely, said Nicole Guiso of the Pasteur Institute, one of the researchers.

The new germ was first identified in France, where more extensive testing is routinely done for whooping cough. The strain now accounts for 14 percent of cases there, Guiso said.

In the United States, doctors usually rely on a rapid test to help make a diagnosis. The extra lab work isn't done often enough to give health officials a good idea how common the new type is here, experts said.

"We definitely need some more information about this before we can draw any conclusions," the CDC's Clark said.

The U.S. cases were found in the past two years in patients at St. Christopher's Hospital for Children in Philadelphia. One of the study's researchers works for a subsidiary of Johnson & Johnson, which makes a version of the old whooping cough vaccine that is sold in other countries.

Jerry Lampen / Reuters file

A young child is vaccinated against the H1N1 flu virus in 2009. A new report says the US childhood vaccine schedule is safe.

It sounds plausible. The average baby gets 24 jabs in 24 months -- needle after needle piercing tender little thighs. Some get as many as five shots in a single doctor’s visit. Surely all this immune stimulation is overloading their little bodies, right?

It’s a seductive idea and one that makes sense, but only to people who don’t study the human immune system. A new report released on Wednesday suggests parents can let go of such concerns.

Nonetheless, government officials need to take these and other worries into account when they design future studies into vaccine safety, the Institute of Medicine committee advised.

“Our committee found no evidence that the childhood immunization schedule is not safe,” Ada Sue Hinshaw, Ph.D, dean of the graduate school of nursing at the Uniformed Services University of the Health Sciences and chair of the committee, told reporters in a conference call.

The Institute, one of the independent National Academies of Science, was asked to look at studies involving not the vaccines themselves, which have been shown numerous times to be safe, but at the schedule for their delivery.

Babies are vaccinated against diphtheria and tetanus, whooping cough and measles, chickenpox and bugs that cause meningitis, pneumonia and diarrhea. Some shots have to be given multiple times over a period of months to fully protect a child, and the schedule is based on when a child becomes vulnerable to infections, as well as when their immune system is developed enough to respond the vaccines.

“A number of concerned parents say the sched­ule is too ‘crowded’ and have requested flexibil­ity, such as delaying one or more immunizations or having fewer shots per visit,” the committee says in its report.

“Some parents have rejected the vaccines outright, arguing that the potential harm of their child suffering a side effect from the vaccine outweighs the well-documented benefits of immunizations preventing serious dis­ease. Other parents delay or decline immuniza­tions due to worries that family history, the child’s premature birth, or an underlying medical condi­tion may make them more vulnerable to compli­cations. Some simply distrust the federal govern­ment’s decisions about the safety and benefits of childhood immunizations.”

And delaying or refusing vaccination can cause harm -- not only to the children who are not fully vaccinated, but to those around them, the committee noted. “States with policies that make it easy to exempt children from immunizations were associated with a 90 percent higher incidence of whooping cough in 2011,” the report says.

The Centers for Disease Control and Prevention says the U.S. is having one of its worst outbreaks of whooping cough in 50 years and that 18 people, mostly very young babies, have died. 

Furthermore, the vaccines have been fine-tuned. "Although the number of vaccinations recommended is greater than ever before, the vaccines used in the current immunization schedule actually have fewer antigens (inactivated or dead viruses and bacteria, altered bacterial toxins, or altered bacterial toxins that cause disease and infection) because of developments in vaccine technology. From 1980 to 2000, the immunization schedule’s total number of antigens decreased by approximately 96 percent," the report reads.

More than 90 percent of U.S. children are fully vaccinated by the time they start kindergarten, but some states, cities and towns have rates below that. Depending on the infection, having less than 80 percent to 90 percent of the population vaccinated can cause outbreaks that endanger infants too young to be vaccinated, the elderly, and people such as cancer patients with suppressed immune systems.

And the report notes that most new parents today are too young to remember disease outbreaks of the 20^th century. More than 16,000 Americans children were paralyzed by polio in the 20^th century. None was last year, thanks to vaccines, the report notes. Smallpox, which once killed a third of its victims, has been completely eradicated by vaccination.

But the National Vaccine Program Office, the Health and Human Services Department agency that commissioned the report, needs to listen more to worried parents, said Dr. Albert Berg of the University of Washington in Seattle, who served on the committee.

“We recognize that parents have some concerns. We should understand those concerns,” Berg said in a telephone interview.

“We should be all on the same side on this topic. We all want a safe and effective vaccine supply.”

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This flu season could be the worst in nearly a decade, health officials warn. Meanwhile, states nationwide are coping with rising cases of whooping cough.

How can you protect yourself and your family? NBC chief science and medical correspondent Robert Bazell hosted a Twitter chat Wed, Dec. 12. Check out the chat at #nbcnewshealth. 

Participating in the chat: Mayo Clinic vaccine expert Dr. Gregory Poland (@drgregpoland); Mayo Clinic infectious diseases expert Dr. Priya Sampathkumar (@PSampathkumarMD);  Mayo Clinic pediatrician and epidemiologist Dr. Young Juhn (@YoungJuhnMD) and Dr. Joseph Bresee, chief of the epidemiology and prevention branch of the Center for Disease Control and Prevention's influenza division.

Follow Robert Bazell on Facebook and on Twitter @RobertBazellNBC.

Expert government advisers want every pregnant woman to get a whooping cough vaccination.

It's only the second time a vaccine has been recommended during pregnancy. Flu shots are also recommended for pregnant women.

The aim of the whooping cough shot is to protect newborns, who are too young to get the vaccine.

The panel's vote was a reaction to the resurgence in whooping cough. The nation is on track to have the worst year for whooping cough since the 1950s. There have been more than 32,000 cases, including 16 deaths, this year.

The Advisory Committee on Immunization Practices approved the recommendation Wednesday. Federal health officials usually adopt the panel's advice and send it to on to doctors and the public.

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How easy is it to avoid getting your kid exempt from school shots? Too easy -- if the epidemic of preventable diseases sweeping through many states are any indication.

It's nearly August and that means the start of school and important vaccine shots for kids entering kindergarten, elementary school or day care. Free, back-to-school immunization clinics are opening up nationwide to provide shots, depending on the state, against a whole range of diseases, including  mumps, measles, rubella (German measles), diphtheria, Hepatitis A, pertussis (whooping cough), tetanus, flu and polio.

What you may not know is that a scary number of these diseases are at epidemic levels in the United States. Whooping cough, an illness that many Americans over 30 thought had disappeared, is at the highest rate among children in the US in fifty years. At least 18,000 cases have been reported in 2012, more than twice as many cases as there were at this time last year. Nine infants have died from whooping cough this year. In addition, an estimated 214 children contracted measles last year in the US, the largest outbreak of a nasty infectious disease in 15 years.

Part of the problem is, too many parents are refusing to get their kids vaccinated against whooping cough and the other horrible diseases that have returned, sickening, disabling and killing children.

There are school requirements for vaccination and, undoubtedly, vaccine rates for most children are still very high. But all states permit exceptions. Two states, Mississippi and West Virginia allow parents to opt-out only on medical grounds -- if the child has an immune disease or is violently allergic to eggs. That seems reasonable.

Other states allow vaccine exceptions for parents who claim religious reasons. While there are few religions that are specifically against vaccines, some states, including Maine, Colorado, Washington, Texas, Vermont, Arkansas and Minnesota, allow parents to say “no” to vaccines for any reason, using a so-called "philosophical" exemption. That is a problem.

California, which has had its own miserable experience the last few years with disease outbreaks and deaths in babies, has one of the easiest vaccine opt-outs in the nation, allowing parents to refuse vaccinations for their children because of personal beliefs. Recently, Democratic state representative, Dr. Richard Pan, proposed a law that requires any parent who wants to send a child to school without the required vaccines to document that they have had a face-to-face conversation with a health care provider about vaccine risks and benefits.

That's a pretty simple law that raises the bar a bit on what can be deadly vaccine exceptions. The bill is in committee, but anti-vaccine groups are buzzing like hornets, looking to get it defeated, as they did with similar efforts in Vermont earlier this year.

In fact, in the name of personal freedom, anti-vaccinators have been pushing to make it easier for parents to opt-out of vaccines in a number of states.

The United States is paying the price in death, disability and misery of allowing anyone who wants to, for no reason supported by medical science, deny vaccines for their children. Vaccine refusers put every other kid, baby and immune-suppressed adult at greater risk of getting infected. Freedom of choice is a great thing -- except when that choice leads to a possibly fatal outcome for your child.

 Arthur Caplan is the head of the Division of Medical Ethics at NYU Langone Medical Center.

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For adults, obesity may increase the risk of catching whooping cough, a new study from Australia suggests.

In the study, obese adults were 50 percent more likely to become infected with whooping cough over a 10-month period compared with those who were not obese or overweight.

Adults were also more likely to catch whooping cough if they had asthma, or were taking medications or supplements, the study found.

Doctors may need to consider targeting adults with these characteristics for whooping cough vaccinations, the researchers said. 

Whooping cough, or pertussis, typically causes the most severe disease in young children, but in recent years, there has been increasing diagnosis of pertussis in adults in some countries, including Australia and the United States. 

CDC: Whooping cough epidemic worst in 50 years

In the new study, Bette Liu, of the University of New South Wales in Sydney, and colleagues analyzed information from more than 263,000 adults ages 45 and older, who were followed for an average of 10 months between 2006 and 2008.

During the study period, 205 adults were diagnosed with pertussis, and 12 people were hospitalized. 

Adults were just as likely to catch pertussis at any age, but those ages 65 and over were more likely to be hospitalized. 

Among those with body mass indexes (BMIs) over 30, the incidence of whooping cough was 133 cases per 100,000 people, compared with 82 cases per 100,000 people for those with a BMI under 25. (People with BMIs between 20 and 25 are considered normal weight; those with BMIs over 30 are considered obese.) 

Those with asthma and those taking medications were 60 percent more likely to have pertussis compared with those without asthma, or those not taking medications. 

Diagnosing pertussis in adults can be difficult because the disease's symptoms such as coughing and fever, occur commonly in other conditions. It is likely that more people were infected than diagnosed, the researchers said. 

It is not clear whether people who are obese, have asthma or take medications are truly more predisposed to pertussis, or whether these people are simply more likely to go to the doctor to be diagnosed, the researchers noted. 

Obesity is known to predispose adults to other respiratory infections, such as pneumonia and the flu, and so it is possible it also increases the risk of contracting pertussis, the researchers said. 

The study was published online July 17 in the journal Clinical Infectious Diseases. 

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• US on Track for Record-High Whooping Cough Rate 

Whooping cough is causing the worst epidemic seen in the United States in more than 50 years, health officials said Thursday, and they’re calling for mass vaccination of adults.

The epidemic has killed nine babies so far and babies are by far the most vulnerable to the disease, also known as pertussis, the U.S. Centers for Disease Control and Prevention says. The best way to protect them is to vaccinate the adults around them, and to vaccinate pregnant women so their babies are born with some immunity.

“As of today, nationwide nearly 18,000 cases have been reported to the CDC,” the CDC’s Dr. Anne Schuchat told reporters in a conference call. “That is nearly twice as many as reported last year. We may be on track for a record high pertussis rate this year,” she added.

“We may need to go back to 1959 to find as many cases. I think there may be more coming to a place near you.”

The last record year was 2010, when 27,000 cases were reported and 27 people died. In 1959, 40,000 cases were reported.

In 2008, whooping cough killed 195,000 people globally, according to the World Health Organization.

Whooping cough is caused by a bacterial infection. It gets its name from the nagging cough it causes that can make children breathless. They often gasp for air, making a distinctive whooping sound. But it’s not so serious in adults and they may not realize that a persistent cough is being caused by pertussis.

Related: Obesity may increase adults' whooping cough risk

Washington state is having an especially bad time with whooping cough this year, with 3,000 cases so far, compared to 20 at the same time last year, said Mary Selecky, secretary of the Washington State Department of Health.  “For every case that we know about, we suspect that there are many people out there who have pertussis and don’t know it,’ Selecky said.

“In many cases, babies get this illness from their mothers or others close to them. It’s absolutely tragic.”

The state has distributed 27,000 doses of a booster vaccine for uninsured adults and has ordered more.  “This disease is very easy to catch,” Selecky said. “It has certainly gotten hold of our population in Washington state.”

The CDC is trying to figure out what's going on, but Schuchat said a couple of factors are clearly at work. The formulation for the whooping cough vaccine was changed in 1997, and kids hitting age 13 and 14 now are the first to have been fully vaccinated with five doses of the new vaccine. The new formulation causes less of a reaction, but it may also wear off sooner, Schuchat said.

The older vaccine was made using a whole pertussis bacterium. It was very effective, but it did cause swelling in some kids who got it, and sometimes caused a fever -- something that scared parents. It also was widely blamed for causing rare but serious neurological reactions, although Schuchat said studies have not confirmed this.

“Vaccines have done a good job of reducing the incidence of pertussis but our vaccines aren’t perfect,” Schuchat said. “We wish we had better ways of controlling pertussis. Given how dangerous pertussis is for babies, preventing infection in babies is our priority.”

Schuchat says people who are not vaccinated have eight times the risk of infection compared to people who are fully vaccinated against whooping cough. And if someone who’s been vaccinated does get whooping cough, the disease is usually less serious and they are far less likely to infect someone else.

The CDC says 95 percent of toddlers aged up to three years have received at least three doses of the vaccine and 84 percent have four doses. And in 2010 69 percent of 13- to 17-year-olds got a fifth booster dose. Kids should get five doses to be fully protected.

And while adults are supposed to have at least one dose of whooping cough vaccine, only 8.2 percent of U.S. adults have done so.

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The U.S. is on course for a record year for whooping cough, health officials said this week. And while vaccinating kids is clearly the most important defense, health experts say adults may not realize they’re supposed to be getting regular shots, too.

Whooping cough, also known as pertussis, is a bacterial infection best known for causing a deep cough in children. They cough so long and so hard that when they can finally catch a breath, they make a distinctive “whoop” sound on the intake. So far this year, the United States has seen more than 16,000 validated cases of whooping cough, said Stacey Martin, an epidemiologist with the Centers for Disease Control and Prevention.

That’s more than the 15,216 cases reported last year. The latest peak was 27,550 cases in 2010, when it killed 27 people, 25 of them babies.

“We are on track to have a record year, I think,” Martin said in a telephone interview.

Pertussis has reached epidemic levels in the state of Washington, with more than 2,700 cases so far this year, and CDC is following outbreaks in 18 other states: Wisconsin, Minnesota, New York, New Jersey, Illinois, Idaho, Montana, Texas, Ohio, Iowa, Missouri, Florida, Arizona, Maine, New Mexico, Pennsylvania, Kansas, and Oregon.

"This time last year we had about 200 cases, which was a lot," said Tim Church, a spokesman for the Washington state department of health. "So to have 2,700 this time is just the most we have seen in my lifetime."

The problem is caused by a number of factors. Babies less than two months old are too young to get the vaccine, so they are especially vulnerable. And the formulation of the vaccine was changed in the 1990s to make it safer, but that also made it a little less effective, Martin said.

“We went to safer vaccine with fewer side effects but the duration of protection is not as good,” she said. Church adds that in Washington state, many parents have opted not to have their children vaccinated -- another factor that could affect the epidemic, although he said there is not data to demonstrate just how badly.

The good news is that 95 percent of U.S. children are vaccinated, Martin says. The bad news is that only 10 percent of adults are.

Children need five doses by age 6 to be fully protected and even then they may need a booster in their teens. Every adult should get at least one dose of the combined tetanus, diphtheria and pertussis vaccine, CDC says in its latest guidelines. The Infectious Diseases Society of America recommends the shot once every 10 years. 

"That’s been our big push in Washington state -- to help adults understand they need to get vaccinated too," Church said.

This is extra-confusing because there are several vaccines on the market, some of which contain just tetanus and diphtheria and some that also protect against pertussis, said Dr. Kathryn Edwards, who directs the Vaccine Research Program at Vanderbilt University in Nashville and who is a board member of the Infectious Diseases Society of America.

To protect the youngest babies, pregnant women should be vaccinated in the later stages of pregnancy, the CDC says. “I think it is hard to vaccinate pregnant women, because pregnant women have this feeling that they aren’t supposed to put anything in their body,” Edwards says. While this is understandable, studies have shown it’s very safe and the mothers-to-be pass on their immunity to their newborns, she said. This is the same for flu, too.

Even health experts often don’t realize the need for adults to be vaccinated. Edwards and colleagues surveyed 1,800 health care workers in 2007, and only 13 percent planned to get a whooping cough shot, with most saying they were unaware they even needed one. Half the time, when babies get whooping cough, a parent is the source, Edwards said. And whooping cough can make adults very sick, as well.

“Adults get whooping cough, and they cough and cough,” Edwards said. The cough can persist for weeks, but doctors and patients alike often don’t even think to check for pertussis. “Certainly, whenever adults need their booster for tetanus and diphtheria, they should include pertussis,” Edwards advised.

It’s not just whooping cough that adults need to be vaccinated against.

The CDC just released updated its adult vaccination recommendations to say adults should think about getting vaccines to prevent a range of diseases: chickenpox; measles, mumps and rubella (German measles); influenza (every single year); hepatitis A and B; and meningitis. Younger adults also need vaccinations against HPV or human papillomavirus, which causes cervical, penis and head and neck cancers (after about age 26 it’s too late), while adults older than 60 need a dose of vaccine against shingles and also should get a shot that protects against a batch of bacterial infections called pneumococcal diseases every five years.

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