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Whooping Cough Vaccination: The Facts and the Truth

Whooping Cough Vaccination: The Facts and the Truth

Posted 4/7/2015

Riley John Hughes died at 32 days from whooping cough complicationsRiley John Hughes died at 32 days from whooping cough complicationsThe tragic death of a baby in Australia was the event that brought whooping cough, or pertussis, to the forefront of my attention recently.

Measles is more of a headline grabber since, fortunately, it's very rare thanks to vaccines. But whooping cough, though relatively uncommon, has never really been brought under control in the same way. It kills around 10 to 20 people a year in the UK and the US, mostly children under 3 months old.

The motivation to write this article came as I heard reports of 19 cases of whooping cough in Utah among children who had all been vaccinated. Numerous anti-vaccine campaigners jumped on this story to claim that vaccines don't work. But the truth, as always, is far more interesting and important to understand.

The reality is that whooping cough outbreaks among vaccinated children are to be expected. It is not that the vaccine isn't effective, the problem is that the immunity it confers wanes with time.

The CDC website has a particularly simple to follow explanation of waning immunity: during the year following full vaccination, 9 out of 10 people will be immune. 5 years later, only 7 out of 10 people will be fully protected. The exact rate at which protection wanes is not yet known for sure, but some studies suggest protection drops off rapidly after 3 years.

The outbreak in Utah confirms that this is a very real problem. The exact ages of the children involved were not reported, but elementary school age is 6-12 years. Under the US vaccination schedule, children receive a booster at around 4-6 years, then don't receive another until the ages of 11 or 12. This is a large gap in the vaccination schedule when immunity can fall away.

In the UK, the last scheduled booster is given at around the age of 3 or 4 and children are left to fend for themselves afterwards.

Knowing all this, it's not surprising that whooping cough continues to plague us. The question is, what is the solution to this problem?

Anti-vaccine campaigners often argue that a vaccine is useless if it isn't perfect so we should stop vaccinating. David Gorski at Science-Based Medicine has rather colourfully described this as the Scotsman fallacy: "If it's not Scottish, it's crap. If a vaccine doesn’t work perfectly 100% of the time, it’s crap. If it isn’t absolutely, positively, 100% safe, it’s crap. If it fails, even just once, to protect against the disease it’s designed to protect against, it’s crap."

This argument fails to acknowledge the startling success of vaccines, even the less effective ones. Since the introduction of the original pertussis vaccine in the 1940s, the US saw the number of cases drop from around 200,000 a year to around 5,000 a year. There has been a sharp upward spike in the last decade back up to 40,000 or so, 2012 being the worst year since 1955, but the effect of the vaccine is still a marked improvement on the figures in the past. The vaccine works, just not perfectly.

Number of pertussis cases in the US, 1922-2010Number of pertussis cases in the US, 1922-2010

Two more appropriate solutions to the waning immunity probelm, which David Gorski carefully describes, are to work to find a better vaccine and to decrease the time between boosters to avoid these "gaps of lesser immunity".

While these are excellent goals, it is unlikely that either of them will happen any time soon. However, this isn't a gloom and doom article. I want to highlight the positive side: the problem is not quite as bad as it might appear.

Vaccines are there to protect the most vulnerable members of society. That is what herd immunity is all about. For whooping cough the most vulnerable are the very young. Even with waning immunity, a 10 year old with whooping cough will normally only suffer from a persistent, irritating cough. If they haven't been vaccinated at all, the cough will most likely be worse and last weeks or even months, with many associated complications, but it's still unlikely to be life-threatening.

The problem is if the infection is passed on to babies, but this is a problem for which there are already good solutions.

In both the US and UK, it is recommended that expectant mothers are immunised against whooping cough when they are around 30 weeks pregnant. This has a dual beneficial effect.

First, mothers are the most common source of whooping cough infection for their baby. As this young doctor recounts, when that happens it is terrifying. Of course, it's good if other people around the baby, such as 10 year old siblings (and maybe even dad!) get boosters to be extra safe.

Secondly, it primes the mother's antibodies and these can be transferred to the baby through the placenta and confer passive immunity to the baby until he or she is old enough to be vaccinated.

The other solution to the problem is to get babies vaccinated on schedule! This passive immunity from mother to baby is only very short term so starting the proper whooping cough vaccinations at 2 months old is important to avoid any gaps in protection.

The truth of whooping cough is that it is not about to leave us alone. But fortunately for most people it is not a life-threatening condition and the vaccines, when administered according to the recommended schedules, give excellent protection to the most vulnerable.

Until we find a way to defeat the disease entirely, though, there will always be tragic deaths. Nothing is 100% certain as nothing can always be as good as the Scottish! But despite their limitations, and so long as those limitations are understood, vaccines really do save lives.