Whooping Cough Vaccine Wanes Over Time

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It’s news that’s certain to ignite debates over vaccines again: researchers say that the childhood immunization against whooping cough fades substantially over time, leaving even fully vaccinated children vulnerable to infection. Weakened protection may be a major contributor to the current outbreak of whooping cough, or pertussis, in the U.S. — the largest in decades — the new study suggests.

In the report, published in the New England Journal of Medicine, Dr. Nicola Klein and her colleagues at the Kaiser Permanente Vaccine Study Center found that the efficacy of the pertussis vaccine declined sharply after children received the last of the five recommended childhood shots, increasing their risk of acquiring the disease by 42% each year. In other words, the study showed, a vaccine that was 95% effective to start would be only 71% effective five years later.

The findings help explain the recent resurgence of pertussis, which has already affected more than 26,000 people this year. Concerns over the vaccine’s effectiveness arose in 2010, when a large outbreak of the disease hit California puzzling scientists, since most of the affected school-aged children had been properly vaccinated. That year, the nation saw 27,550 cases of pertussis overall, the highest since 1959. Another outbreak in Washington state earlier this year only heightened the concern. Although 2012 should have seen a natural downswing in the cyclical pattern of the disease, it’s on track to be the worst year yet.

(MORE: How Safe Are Vaccines?)

To better understand the increasing rates of disease, Klein and her group turned to Kaiser’s population of managed care members, focusing on children ages 4 to 12, who were enrolled in Kaiser’s health plan in northern California in 2006 to 2011. The researchers compared 277 fully vaccinated children who tested positive for the pertussis, which is caused by the Bordetella pertussis bacterium, witht two control groups: one that included 3,318 children who tested negative for the microbe and another group of 6,086 children who were not tested for the disease. The second control group allowed the scientists to adjust for any lifestyle or behavioral factors that might account for some families’ better access to testing or health care services.

All children received all five doses of the pertussis vaccine, known as DTaP (for diphtheria, tetanus and acellular pertussis). The researchers looked specifically at the time between the last dose — given between ages 4 and 6 — and the onset of disease in children who acquired pertussis, and found that indeed, they were more likely to have experienced more lag time. Children who tested positive for pertussis had received their last DTaP dose 1,699 days earlier, compared with 1,028 days for those testing negative.

“We found a substantial waning in protection in the five years after the fifth dose,” says Klein, adding that the findings do not suggest the current vaccine is useless. “We also found was that some protection is better than no protection. The existing DTaP is safe and effective, but protection just doesn’t last as long as we’d like.”

Although the vaccine’s effectiveness weakens over time, the protection it offers is still critical for maintaining enough population-based immunity to safeguard infants, who are too young to be vaccinated against infection. Health experts stress that parents should not to stop vaccinating their kids just because the immunizations appear to lose their effectiveness.

(MORE: Vaccine Safety: New Report Finds Few Adverse Events Linked to Immunizations)

The DTaP vaccine, which uses purified snippets of the pertussis microbe to trigger immunity, was first introduced in the U.S. in 1991. It replaced the older immunization developed in the 1940s, which used whole, killed B. pertussis cells. Adverse reactions to that vaccine, including high fever and some neurological symptoms, led to the switch.

The problem was that health officials began to see an increase in cyclical outbreaks of pertussis, occurring every three to five years, among children who were properly vaccinated using DTaP. As these reports, suggesting a weakening of DTaP’s effectiveness, began to build, the Centers for Disease Control and Prevention (CDC) recommended in 2005 that people 11 years old or older receive a sixth dose, or booster, with the Tdap vaccine, which is designed for teens and adults, to bolster their defenses against the bacterium.

Was this waning efficacy known at the time that DTaP was licensed? “No,” says Dr. Tom Clark, medical epidemiologist at the CDC. “Vaccines are studied extensively in thousands of kids before they are licensed. But we never really know what is going to happen until we implement immunizations on a public health scale. We never expected we would be doing these kinds of vaccine effectiveness studies on vaccines that we’ve been using for 20 years.”

Vaccine studies evaluated by health experts before licensing often don’t follow participants for very long, however, says, which means that the true effectiveness of immunizations over time is often not learned until they become part of the vaccine schedule.

There were hints that the newer, acellular version of the vaccine was slightly less effective than the older shot, says Dr. Kathryn Edwards, chair of pediatrics at Vanderbilt University and a member of the American Academy of Pediatrics’ Committee on Infectious Diseases, who was part of the initial studies on the DTaP vaccine, but the tradeoff in fewer adverse reactions was worth the switch. “It was clear in those studies conducted in the 1990s that the whole cell vaccine was still better than the acellular vaccine,” she says. “But by and large the acellular was 85% effective, and was much safer.”

(MORE: Vaccine Safety: Why Parents’ Alternative Immunization Schedules May Cause Harm)

Health experts point out that the current study did not look at DTaP’s effectiveness per se; rather, it assessed the risk of pertussis among a vaccinated group of children. The burden of disease in the Kaiser population could have been higher than average, notes Edwards. In that area of northern California, about 11% of children either aren’t vaccinated at all or only partially immunized against pertussis, and that may increase children’s exposure to the bacterium. Couple that with the fact that the DTaP vaccine isn’t 100% effective — no vaccine is — conferring only about 85% protection, and it’s not that surprising that immunity starts to falter.

Nevertheless, the findings reveal a weakness in the pertussis vaccine that public health experts will have to address. It’s not clear how much added protection the Tdap booster provides, but for now, it’s a stopgap measure to protect against infection and spread of the disease. “We do think that the long-term answer is to find a new vaccine that provides long-lasting immunity,” says Klein.

MORE: Exposure to Common Chemicals May Weaken Vaccine Response

Alice Park is a writer at TIME. Find her on Twitter at @aliceparkny. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.

20 comments
tatsu15
tatsu15

Children have an immune system that needs to develop. Germs and viruses will help build them. Vaccines make their immunity too sterile... more cases of autoimmune disease, asthma and allergies due to this. Also, vaccines seem to bypass the body's initial defense mechanisms. Instead of being exposed through nose, mouth, ears, the vaccines are directly injected into muscle tissue and sort of shocks the immune system. This can trigger miscommunication esp. if many types of vaccines are given. 

Anti-bacterial soaps are another culprit for outbreaks as well.

Kenny Lydall
Kenny Lydall

No - they don't say it! My guess was wrong!

Not surprised the 'study' didn't control for the vaccination it's self - they never do. 

morningdove
morningdove

How CONvenient to say that chemicals weaken vaccines and that vaccines weaken over time. The truth will out that vaccines do not work, never have never will. The answer is clean water, nutritious food, rest, fresh air, sunshine and moderate exercise that all strentghen our immune systems. Vaccines are a cash grab that is harming our children. When will we stop listening to lies and use our common sense about health. We look for the easy answers at our own peril. We have to take care of ourselves and the planet we live on. This requires a lot more work - a pill or vaccines is not going to keep us from getting sick. We have to care and do what it takes to stay healthy.

Timothy Hawkins
Timothy Hawkins

A basic course in microbiology and/or immunology would help educate you on the importance of vaccines. 

morningdove
morningdove

I have done extensive research on vaccines and there are a lot of cons to taking them that are not discussed openly and honestly by pro-vaccination people. That leads me to suspect that the problems are even worse and that they are being hidden. The PR story is dishonest and does not provide people with informed choice. There are side effects to vaccines - there are some vaccines that should only be by choice such as gardasil. Anything that is not upfront and honest especially when it comes to our health has problems and the vaccine industry sure fits that picture.

Anne G
Anne G

As of right now, Gardasil is still given by choice. I don't think it is necessary to give it to a 9-year-old, though. I personally will not let my daughter get it until she is 18. At that point, it will be her choice.

Kenny Lydall
Kenny Lydall

Before I even read the article - let me guess, the answer is yet more vaccines.

Anne G
Anne G

Oh here we go with the anti-vaccine, tin foil hat-wearing vaccine conspiracists. Do a search for "sounds of whooping cough" and see if you still want to refuse to vaccinate your kids against it. Vaccination should be mandatory under federal law. Parents who refuse to vaccinate for non-medical reasons, and/or disciples of Jenny McCarthy and her ilk, should be jailed and have their kids taken away. Period. I am pro-vaccine and my daughter has received all required shots. She is healthy, active, and intelligent.. shocking, I know! The vaccines did not give her autism- amazing, isn't it??

morningdove
morningdove

Wait until she is older and see what the long term damage is.

Anne G
Anne G

I don't appreciate you saying that my child is damaged.

morningdove
morningdove

I hope that your child has not been harmed by these vaccines but I would ask myself why is my child subjected to taking so many more vaccines than in the 60's. I had the mumps, measles, flu and I am alive and well. I am concerned that the vaccine companies do not talk about the side-effects of their needles or what is in them. Have you done the research of what is in these vaccines and how many needles do the drug companies say are necessary for immunity and now they say they wear out? - what are you going to do give your child more vaccines. Please do the research. Look up Doctor Tenpenny. There is something wrong with the amount of needles that children are required to take for illnesses that are not fatal. 

Timothy Hawkins
Timothy Hawkins

Long term damage from vaccines? Based on what evidence? It's far riskier to go without vaccines and run the risk of either 1) catching a vaccine-preventable disease or 2) potentially spreading that disease to immuno-comprised people (infants, elderly, and the very sick).

morningdove
morningdove

Many diseases such as mumps, colds, flu do not kill people. What kills people is poverty. A nutritious diet, clean water, fresh air, sunshine and exercise will build a strong immune system and if one does catch something with rest, sleep, proper nutrition staying hydrated and well nourished will minimize symptoms and ensure a speedy recovery. Poverty and the lack of access to food water and proper housing is the problem that vaccines will never solve. As for long term damage nobody knows yet what it is -  drug companies sure are not looking. Only time will tell but logically injecting thiomersal (Mercury), formaldhyde and viruses into people will have some long term effect.

Always Sick Chick
Always Sick Chick

You didn't cover the fact that decreased vaccination among children has contributed to these outbreaks either.  If everyone was getting vaccinated, these outbreaks wouldn't be as large or severe.

Jack Stone
Jack Stone

Vaccines are a big lie...they are not as safe or as effective as claimed or there would not have been any need to excempt vaccine injuries from litigation to both the MD and the vaccine manufacturer. What other dangerous class of drug has this kind of protection? The answer is none, and there are many deadly drugs on the market. Best way to protect your kids is to make sure they are nutritionally sound, get plenty of sleep, exercise and sun. Tell the pediatricians to stuff it.

Anne G
Anne G

Sure, why not take your next vacation in India or somewhere like that so your kids can catch polio "naturally"? No harm in that, right? They might be paralyzed for life, or even die, but you can sleep soundly at night knowing that you did not let them get "dangerous" vaccines! 

Sarah Hanviriyapunt
Sarah Hanviriyapunt

Oh yes! And so we need to inject MORE foreign DNA/protein into our tissues/bloodstreams so that then the vaccines will work? I don't think so. Not me or my children. Take extra vitamin D, eat healthy, and you won't get sick; I don't care what disease it is. The drug companies have touted these as being responsible for all these diseases disappearing.

http://www.doctoreisenstein.co...

Patrick McGean
Patrick McGean

In my opinion vaccinations are a dreadful lie, it is not the pathogen, it is our terrain.

Autism and Alzheimer's are some of the collateral damage of vaccines, and this article points out vaccines don't do what they are advertised to do.  Why do people get sick after being vaccinated, it must be the unvaccinated?  Fear is the great motivator for stupidity.

Add organic sulfur to your diet and the increased cellular oxygen will deal with the

infections, even if you are so fearful to vaccinate.

Cellular Matrix Study