Tag: pertactin

Can Vaccinated Children Be Asymptomatic Carriers of Pertussis?

Why do anti-vaccine folks like to talk about baboons so much?

“Did you know that a study showed that baboons injected with whooping cough vaccine became infected with whooping cough anyway – and silently spread the disease to other baboons for 35 days?”

Anti-vaccine Meme

Is it because baboons are used in the study of vaccines?

That’s part of it, at least when they can find a study where they can cherry pick the results to suit their needs.

The Baboon Study

Like most anti-vaccine talking points, this one about baboons, has some truth to it.

An adult male baboon.
An adult male baboon. Photo by Elizabeth Miller

There was a baboon study with the pertussis vaccine and it found that previously vaccinated baboons could develop asymptomatic carriage of the pertussis bacteria after they were intentionally infected.

Here is where it is important to note that an infection is different than a disease.

The example that many people are familiar with is tuberculosis. It is common to have a TB infection without any signs or symptoms and to not feel sick. The only reason we know that they have TB is because they had a positive TB test.

Unfortunately, about 5 to 10% of these people with TB infections can eventually develop TB disease, with coughing, weight loss, night sweats, fever, and chest pain, etc.

It is kind of the same with the baboons in the study. Twenty-four hours after two previously vaccinated baboons were inoculated with pertussis bacteria in the back of their nose and trachea, an unvaccinated baboon was put in each of their cages.

The vaccinated baboons continued to have pertussis bacteria in their noses, which the researchers had put there, for up to 35 days. And they were able to eventually pass the pertussis bacteria to the unvaccinated baboons in their cages. Vaccinated baboons also became infected or colonized after they were put in a cage with an intentionally infected unvaccinated baboon.

“…animals did not cough and showed no reduction of activity, loss of appetite, or other outward signs of disease.”

Warfel et al on Acellular pertussis vaccines protect against disease but fail to prevent infection and transmission in a nonhuman primate model

The vaccinated baboons were infected, but they never did develop symptoms of pertussis.

What Does The Baboon Study Mean?

One thing that is for sure – the baboon study found that the pertussis vaccines work. Only unvaccinated baboons got sick with pertussis.

But does this study explain our current outbreaks of pertussis?

Are vaccinated people becoming colonized and then getting others sick?

I guess it is possible, but we are not baboons in a cage with other baboons. How would we spread a respiratory disease, even if we did become colonized with the bacteria, if we don’t have symptoms?

It may explain part of our outbreaks though.

If vaccinated people do commonly become colonized with pertussis bacteria, then they might very well test positive for pertussis even though they don’t have symptomatic pertussis disease. So when they develop a cold or bronchitis and are found to have a positive pertussis test, then couldn’t that test just indicate that they have a pertussis infection and not disease, even though something else is actually causing their symptoms?

That’s what we think happens with strep carriers, right?

That’s kind of what the baboon study found. All of the baboons tested positive, but only the unvaccinated baboons had symptomatic pertussis disease.

“Baboons vaccinated with wP vaccines exhibit a level of protection that is intermediate between convalescent animals and aP-vaccinated animals. They exhibit no outwards signs of disease and are initially colonized to the same high level as aP-vaccinated animals but clear the infection more rapidly.”

Pinto et al on Pertussis disease and transmission and host responses: insights from the baboon model of pertussis.

It is interesting to note that the baboon study also found that baboons who had received whole cell pertussis vaccines also became carriers. They just didn’t stay carriers for as long as the baboons who got the newer acellular pertussis vaccine. But since they were still carriers, if asymptomatic transmission is such a big problem, wouldn’t it have been a big problem back in the day when everyone got whole cell pertussis vaccines?

The Debate Over Asymptomatic Carriage

Most vaccines prevent the spread of disease.

Do the pertussis vaccines?

Most folks still think so.

“The baboon model pioneered by Warfel et al. is without question a game-changer, shedding light on the impact of vaccination on disease and infection. However, the view it affords is clearer with respect to immunity and pathology than with respect to transmission. We point out that the extrapolation of the possibility of transmission from vaccinated baboons in the laboratory to the probability of transmission from vaccinated humans in the population is unwarranted. More work is needed to elucidate the relative transmissibility of infections in vaccinated vs. unvaccinated hosts. The evidence adduced above suggests, however, that vaccination with aP must have a strong effect on transmission as well as disease.”

Matthieu Domenech de Cellès et al on Epidemiological evidence for herd immunity induced by acellular pertussis vaccines

Even the author of the baboon study has said that “We agree that these data should not be directly extrapolated to pertussis transmission in humans. Although baboons are >96% genetically similar to humans, there are likely differences in how the species respond to vaccination and infection. We also agree that aP-vaccinated infected people are likely less efficient at transmitting pertussis compared with unvaccinated infected people, although it is not clear to what extent.”

Others think that asymptomatic carriage of pertussis might behind a lot of our recent outbreaks. Or at least what helps them grow so large.

Still, it is important to remember that unvaccinated folks do play a role in these outbreaks too. In a pertussis outbreak at a Florida preschool, in which most kids were vaccinated, the outbreak was started by a vaccine-exempt toddler.

And we have seen this in many other areas and it has been confirmed by many studies. Whatever else is contributing to pertussis outbreaks, like waning immunity, they are also associated with vaccine refusal.

“Counties with higher exemption rates had higher rates of reported pertussis among exempted and vaccinated children when compared with the low-exemption counties.”

Imdad et al. on Religious exemptions for immunization and risk of pertussis in New York State, 2000-2011.

But what if the DTaP and Tdap vaccines do cause folks to be asymptomatic carriers?

Even if that is true, understand that these vaccines don’t actually infect you, making you a carrier. They just might not prevent you from becoming a carrier if you are exposed to someone else with pertussis. While that might be a good reason to develop a new and better pertussis vaccine, it certainly isn’t a reason to skip or delay your child’s vaccines now.

Remember that even with our current outbreaks, rates of pertussis were much higher in the pre-vaccine era.

What to Know About Vaccines and Asymptomatic Carriers of Pertussis

The role of asymptomatic carriers and pertussis is controversial, but it certainly isn’t a reason to skip or delay your child’s vaccines.

More on the Vaccines and Asymptomatic Carriers of Pertussis

Vaccine-Driven Resistance of Bacteria and Viruses

It is well known that bacteria and viruses can become resistant to antibiotic and anti-viral drugs.

From amoxicillin for Streptococcal pneumonia infections to amantadine for the flu, resistance is a growing problem that is limiting how easily we can treat many infections.

Vaccine-Driven Resistance of Bacteria and Viruses

Since bacteria and viruses seem to have such an easy time developing resistance against commonly used drugs, do we see the same thing with vaccines?

Fortunately, no.

We do not see bacteria or viruses creating resistance in our vaccines so that they no longer work.

For example, despite what you may hear, the MMR vaccine still prevents all wild strains of measles.

What about the pertussis vaccine and the fact that we are finding more and more strains of pertactin-negative pertussis bacteria? Doesn’t that mean that the Bordetella pertussis bacteria have mutated and are causing a pertussis resurgence because they are resistant to the vaccine?

While an interesting theory, pertactin is only one of the components (antigens) of the pertussis bacteria that are in pertussis vaccines that help them to induce immunity. Others can include filamentous hemagglutinin, chemically or genetically detoxified pertussis toxin, and fimbrial-2 and fimbrial-3 antigens.

So no, pertactin-negative pertussis bacteria are not driving outbreaks of pertussis or whooping cough, and they have not become resistant to pertussis vaccines.

Vaccine-Induced Pathogen Strain Replacement

What about the fact that we sometimes seen a rise in new bacteria once a vaccine wipes out the bacteria it works against?

While this type of vaccine-induced pathogen strain or serotype replacement can happen, it is not because the bacteria develop any kind of resistance. Some vaccines can only target specific strains of a virus or bacteria. The latest version of Prevnar, for example, can prevent the 13 strains of Streptococcal pneumonia that are most likely to cause disease in children. That leaves out over 75 other strains.

And the Hib vaccine only prevents Haemophilus influenzae type b infections. There are five other H. flu serotypes (a-f) and other non-typeable strains that aren’t covered by the Hib vaccine.

The same goes for the meningococcal vaccines. None of them cover all meningococcal serotypes.

Isn’t it just as bad if one of those other strains starts growing after your kids are vaccinated?

While it certainly sounds bad, as it seems like you are just replacing one bacteria for another, it really isn’t.

Rates of invasive pneumococcal disease have decreased dramatically since Prevnar was introduced.
Rates of invasive pneumococcal disease have decreased dramatically since Prevnar was introduced. Photo courtesy of the CDC.

Why not?

Because the replacement bacteria are often much less likely to cause invasive disease and the levels of disease they do cause don’t come anywhere close to pre-vaccine levels.

Vaccines work, even when something like vaccine-induced pathogen strain replacement happens.

Vaccines Can Help Prevent Drug Resistance

If you are really concerned about antibiotic resistance, you would want more people vaccinated.

Not only do vaccines not lead to an increase in vaccine or drug resistant bacteria or viruses, but they can help us fight the growing problem of drug resistance.

“Vaccinating humans and animals is a very effective way to stop them from getting infected and thereby preventing the need for antibiotics.”

WHO on Why is vaccination important for addressing antibiotic resistance?

Consider all of the people who take Tamiflu or antibiotics when they get the flu because they didn’t get a flu shot?

Or how many antibiotic prescriptions haven’t been written because kids did get vaccinated with Prevnar and never got an ear infection, pneumonia, or meningitis?

Vaccines in the pipeline could help even more.

What to Know About Vaccine-Driven Resistance

Vaccines are not causing an increase in vaccine-resistant bacteria or viruses and can actually help us fight the growing problem of antibiotic resistant bacteria.

More About Vaccine-Driven Resistance

Do Pertussis Vaccines Work Against Pertactin-Negative Pertussis Bacteria?

Whooping cough is back!
This is not the first time that whooping cough has come back. We also saw a rise when folks got scared to use the DTP vaccine in the 1970s and 80s.

Pertussis vaccines aren’t perfect.

Few people claim that.

But what’s the problem with them?

Most experts think that the main issue is waning immunity.

While the acellular pertussis vaccines (DTaP and Tdap) that replaced the more effective whole cell pertussis vaccine (DTP) do work, the immunity they provide does not last as long as we would like.

They still work better than not getting vaccinated at all though.

Pertactin-Negative Pertussis Bacteria

What about the fact that we are starting to find pertactin-negative pertussis bacteria?

Does that mean that Bordetella pertussis, the bacteria that cause pertussis or whooping cough, have mutated and are causing a pertussis resurgence because they are resistant to the vaccine?

“CDC is currently conducting studies in the United States to determine whether pertactin deficiency is one of the factors contributing to the increase in the number of reported pertussis cases. CDC will continue to closely monitor the situation and evaluate all available scientific evidence before drawing any conclusions. There is also no suggestion that these new strains are causing more severe cases of pertussis.”

CDC on Pertactin-Negative Pertussis Strains

While an interesting theory that the anti-vaccine movement has latched on to, the answer seems to be no.

While pertactin-negative pertussis are certainly a thing, there is already evidence saying that they are not driving pertussis outbreaks – evidence that anti-vaccine folks like to ignore:

  • pertactin is only one of the components (antigens) of the pertussis bacteria that are in pertussis vaccines that help them to induce immunity. Others can include filamentous hemagglutinin, chemically or genetically detoxified pertussis toxin, and fimbrial-2 and fimbrial-3 antigens.
  • pertussis vaccines continue to be effective against pertactin-negative Bordetella pertussis bacteria
  • pertactin-negative Bordetella pertussis bacteria have not been found in all areas experiencing outbreaks of pertussis, as you would expect if they were driving these outbreaks
  • the first pertactin-negative Bordetella pertussis bacteria were found as early as the 1990s, long before we started using the current acellular versions of pertussis vaccines and before we started seeing an increase in outbreaks.

Also of note, pertactin-negative Bordetella pertussis bacteria do not cause more severe symptoms than pertactin-positive bacteria.

“Although pertussis vaccines aren’t perfect, vaccination remains our best prevention tool and we should continue to maintain high levels of DTaP coverage among children, sustain Tdap coverage in adolescents and increase Tdap coverage in adults and pregnant women. ”

CDC on Coughing up the Facts on Pertussis

Most importantly, it should be clear that pertussis vaccines work as we are not seeing pre-vaccine era levels of pertussis, even as we do see some outbreaks.

What To Know About Pertactin-Negative Pertussis

Pertactin-negative pertussis bacteria are not driving outbreaks of pertussis or whooping cough, and they have not become resistant to pertussis vaccines.

More About Pertactin-Negative Pertussis Bacteria