Does the pertussis vaccine work?

[littlec]

If we judge the effectiveness of the vaccine by the decline of the disease, then by that standard, the pertussis vaccine does not work at all, since the cases have risen tremendously in the past 20 years, with only a few years that it's gone down.

http://www.cdc.gov/vaccines/pubs/pin...G/coverage.pdf

http://apps.who.int/immunization_mon...ntry.cfm?C=USA

The vaccination rate has been over 90% for DTaP since 1994, yet Pertussis has risen almost every year since 1980, and it's much higher now than it was back then when vaccination rates were lower. Can someone explain how anyone believes this vaccine works? Maybe I'm reading wrong or misunderstanding, I don't know. It just makes no sense to me. Thanks.

[CookAMH]

To me, and from the reading I have done, it's one of the least effective vaccines. I'd say 50% at best. So then I conclude, why bother?? (and we don't bother...)

[AFWife]

It's been said again and again: It doesn't do ANYTHING for transmission (like you'd think a vax would) All it does is lessen symptoms.

So, instead of Person A getting pertussis and staying home because they're REALLY sick they get a moderate cough (that is usually diagnosed as bronchitis) and they go and spread it around. All of those "scare commercials" where they tell parents to be vaxed for the sake of their baby is bogus because vaxing the parent really does nothing to protect the baby.

[ema-adama]

Yes, it depends on what you mean by 'works'.

No it does not prevent transmission, making it little more than a hopeful attempt to control transmission by vaccinating new parents.

It does lessen severity in recently vaccianted individuals.

[heathergirl67]

The DTaP vaccine is 95% effective in preventing all three diseases that it immunizes against—diphtheria, tetanus and pertussis. It is 59-89% effective in preventing pertussis, while the protection rates for diphtheria and tetanus are higher. Pertussis occasionally occurs in children who have received the pertussis immunization, but it is less severe and has fewer complications.

http://www.immunizationinfo.org/vacc...whooping-cough

In household outbreaks of pertussis, children <5 years of age who received at least 3 doses of vaccine had 12% less clinical disease; vaccinated cases were 63% less culture-confirmed and transmitted infection to 62% fewer contacts. Three doses of pertussis vaccine are likely to decrease circulation of Bordetella pertussis by reducing the proportion of bacteriologically positive cases and transmissibility

http://www.ncbi.nlm.nih.gov/pubmed/16940847

In Brazil until 2004, pertussis whole cell vaccine was given at 2, 4 and 6 months of age and a booster dose was given between 15 and 18 months of age. In the study area, pertussis vaccine coverage for 3 doses among children younger than one year of age was higher than 96%. The study of vaccine effectiveness in contacts revealed a low vaccine effectiveness against clinical disease, 12.5% (compared to children who received one dose only). On the other hand, vaccine effectiveness in reducing the transmissibility of a vaccinated primary case aged 7 months to 5 years old was 61.6%. This may have a significant effect in reducing circulation of B. pertussis in the studied population

http://www.biomedcentral.com/1471-2431/7/21

[ema-adama]

I understand that you believe that the DTaP prevents transmission.

Do you have the full article for the study published in 2006 in Brazil? I am curious to see the study design. The third link is quoting the same study from the second link.

From the 3rd link.

Pertussis is an endemic disease, with peaks every three to four years worldwide. Incidence of pertussis has declined, however many cases of pertussis may be underreported or not diagnosed.

If a disease in endemic despite high vaccination rates, it points to the vaccines not preventing transmission.

The issue of diagnosing the disease, both in vaccinated, undervaccianted and unvaccianted makes it impossible to know what the real disease burden is. Knowing that there will be a peak every three to four years, you would expect an outbreak every three to four years irrespective of vaccine uptake.

There are a variety of theories as to why the DTaP is not working at preventing the spread of the disease. The fact remains, it is not preventing the spread of the disease. It is modifying the disease in persons who have been vaccianted.

[heathergirl67]

Actually I don't necessarily believe that DTaP prevents transmission. Those are some articles that claim that they do. And it seems that from the numbers there is often less pertussis reported once vaccination occurs. But then there's other equally reputable studies that say it is not helpful in reducing transmission. Honestly it kind of confuses me. I was just presenting some of the other arguments, especially those that have me scratching my head.

BTW, thanks for catching my mistake on the other thread so that I could move it over here.

[Sileree]

The authors of this study noticed that vaccine effectiveness was reported to be greater in children treated by physicians who ignored mild coughing illnesses and only sent in swabs or blood samples of children with typical pertussis symptoms to a lab. So they categorized the doctors by how compliant they were to try to control for bias.

Using the WHO case definition that required at least 21 days of cough with coughing spasms, whooping and vomitting (the typical pertussis symptoms), the effectiveness of DTaP was 69% in the high compliance group and 86% in the low compliance group.

But, using a case definition that included both mild (coughing at least 7 days) and typical pertussis, the effectiveness of DTaP was 40% in the high compliance category and 75% in the low compliance group.

So they conclude:

"Our data suggest that observer bias can significantly inflate calculated vaccine efficacy. It is likely that all recently completed efficacy trials have been effected by this type of observer bias and all vaccines have considerably less efficacy against mild disease than published data suggest."

http://pediatrics.aappublications.or...ract/104/4/997

So IMO, it works, but not as well as pro-vaccine groups like the CDC say it does ("It is 59-89% effective in preventing pertussis.") They don't mention that the WHO definition is not all that accurate.

[amnesiac]

Moving to the main forum.

[Pirogi]

Originally Posted by Sileree

The authors of this study noticed that vaccine effectiveness was reported to be greater in children treated by physicians who ignored mild coughing illnesses and only sent in swabs or blood samples of children with typical pertussis symptoms to a lab.

That reminds me of the decrease in polio ... after they changed the definition of polio.