Category Archives: Vaccines

WDDTY on the anti-vaxx band-waggon

WHAT DOCTORS DON’T TELL YOU (WDDTY) is probably the most vile publication I know. It systematically misleads its readers by alarming news about this or that conventional treatment, while relentlessly promoting pseudoscientific non-sense. This article , entitled “MMR can cause skin problems and ulcers if your immune system is compromised” is a good example (one of a multitude)…

Source: WDDTY on the anti-vaxx band-waggon

Woman who died from measles had been vaccinated

WDDTY headline with obligatory scary needle shot.
WDDTY headline with obligatory scary needle shot.

The Holy Trinity of anti-vaccinationists runs thus:

  1. Vaccines are dangerous.
  2. Vaccines don’t work.
  3. Vaccine-preventable diseases aren’t serious anyway.

And when one is rebutted they move to another, frequently in rotation, perennially moving the goalposts.

What WDDTY Don't Tell You about infectious disease.
What WDDTY Don’t Tell You about infectious disease when there is no vaccination.

Still, deaths from preventable disease are the anti-vaccinationist’s worst nightmare. Their narrative can only succeed in an atmosphere where the realities and consequences of preventable disease are a distant memory. We do recommend you watch The Vaccination Chronicles by Australian skeptic and all round good egg Richard Saunders.

Provable deaths in the newspapers are the ultimate heresy to the antivax cult. You need only look at the torrent of vile abuse heaped on the parents of Dana McCaffery by Australian antivax whackaloon Meryl Dorey. Your child died of vaccine preventable disease? Off-message. STFU.

So it is with the recent death of an American woman from measles.

The first death in 12 years from measles was reported last week from the USA, which had doctors emphasising the important of vaccination. However, what doctors didn’t tell you was that the woman who died had been given the MMR vaccine.

What they did tell you, however, was that she was immunocompromised, and thus in the high risk group for exposure to measles, a highly contagious disease. Hilariously, WDDTY try to spin this as an anti-pharma angle:

It’s believed the woman caught measles when she was in hospital, and she died because her immune system had been seriously compromised from too many pharmaceuticals.

Let’s get this straight, Lynne: you have no fucking clue why she was immunocompromised. She was on immunosuppressant drugs, there are a number of reasons for using these including transplants, rheumatoid arthritis, Crohn’s disease, control of severe allergic asthma.

The immune system is a complex beast and when it works against you, as it does in autoimmune disorders, you can suffer dramatic and life threatening symptoms.

All in all it’s just as well that all those products you pimp for “boosting your immune system” do no such thing. If they could, they would be dangerous.

Doctors at the hospital in Washington state, where she died, confirmed she had had the MMR vaccine when she was a child. One, Dr Jeanette Stehr-Green, also said on local TV that the woman had been taking medication that had interfered with her immune system, and made her more vulnerable to the measles virus.

Right, so you assumed that she was actually taking “too many pharmaceuticals” when actually you (and we) have no idea at all of her health history or the reason she was on immunosuppressant therapy. But you assume… What? That the doctors put her on it on a whim? Fatuous.

The hospital has refused to reveal the age of the victim, but have said she was not elderly.

Indeed. Measles kills indiscriminately, including years after the event due to subacute sclerosing panencephalitis. Odd that something as natural as measles turns out to be a real bastard. And don’t pretend you don’t know about SSPE: in October 2007, WDDTY said:

Latent infections also lie at the root of a number of serious chronic diseases that are dependent upon the immunological response, including progressive multifocal leucoencephalopathy, a rapidly progressing neuromuscular disease, and subacute sclerosing panencephalitis, a rare progressive brain disorder caused by an abnormal immune response to the measles virus. In fact, the latter is thought to be triggered, in some cases, by the MMR vaccine.

You cited this source: Latent Virus Infections. See where it mentions immunisation as a source of SSPE? Me neither. Of course nobody has ever checked this, have they? Oh, wait, yes they have:

For situations where cases of SSPE occur in vaccinated individuals who have no previous history of natural measles infection, the available evidence points to natural measles infection as the cause of SSPE, not vaccine.

WHO, Jan 2006.  And while it might be charitable to attribute your ignorance of the falsity of your claim, it would also be incredibly naive.

Mind you, that’s pretty tame. In September 1994 you said:

Besides causing dangerous mutations like atypical measles, the measles portion of the [measles] vaccine has been associated with numerous side effects, including nerve deafness, encephalitis, epilepsy, febrile convulsions, Guillain-Barre Syndrome (a paralysis) and subacute sclerosing panencephalitis (SSPE), a fatal wasting disease rarely associated with measles .

That was characteristically inaccurate, in that these things have “been associated” primarily by anti-vax cranks.

What does the reality-based community say? Two thirds of people with Guillain–Barré syndrome have experienced an infection before the onset of the condition, usually gastroenteritis or a respiratory tract infection. Vaccines can prevent some causes of these. In many cases the exact nature of the infection can be confirmed: approximately 30% of cases are provoked by Campylobacter jejuni bacteria, which cause diarrhea. A further 10% cases are attributable to cytomegalovirus (CMV, HHV-5). Despite this, only very few people with Campylobacter or CMV infections develop Guillain–Barré syndrome (0.25–0.65 per 1000 and 0.6–2.2 per 1000 episodes, respectively).[1] The strain of Campylobacter involved may determine the risk of GBS; different forms of the bacteria have different lipopolysaccharides on their surface, and some may induce illness while others will not.

While rare cases of GBS have been reported following flu vaccination, a link with measles virus is explicitly ruled out in “Pediatric Guillain-Barré syndrome”. Current Opinion in Pediatrics 25 (6): 689–693. doi:10.1097/MOP.0b013e328365ad3f

On we go:

She was receiving hospital treatment for several health problems when she caught measles from another patient. As her symptoms worsened, she was taken to the University of Washington Medical Centre in Seattle, where she died from pneumonia due to measles last spring.
Doctors did not establish the cause of death until the autopsy was carried out, as the woman did not display any of the usual symptoms associated with measles, such as a rash.

Yup. Rare, but not unheard of especially in the immunocompromised. It’s quite likely that there have been other deaths that were never identified as being due to measles, because these patients are by definition very sick anyway.

No other patient developed the disease, and the hospital is confident the outbreak has been contained.

Good, but it should never have had to be contained.

Measles cases showing uptick due to antivaccinaitonists.
Measles cases showing uptick due to anti-vaccinationists.

Measles vaccination rates declined due to anti-vaccination activists and especially the fraudulent work of Andrew Wakefield. As rates dropped below the levels required for herd immunity, measles infection rates rose.

Antivaxers are responsible for the greater prevalence of measles. Antivaxers are responsible for its return from near-eradicated status in the 1990. Antivaxers are responsible for the fact that the virus can circulate among a larger pool of people who are not immune. The unvaccinated are much more likely to contract measles than the vaccinated.

Family launching enquiry into mysterious death of anti-vaccine doctor

WDDTY is part of the counter-factual counter-culture that is the anti-vaccination movement. An antivax doctor kills himself as the feds move in on his fraudulent empire? It must have been black helicopters.

Mystery surrounds the sudden death of Dr Jeff Bradstreet, a high-profile anti-vaccine campaigner who treated autistic children. His body was found in a river in North Carolina, with gunshot wounds to his chest, a week after his clinic had been raided by Food and Drug Administration (FDA) agents.

Mystery? Not really. While there is ample documentation of conspiracist rumours following his death, there’s no real mystery. He used real therapies with real possibilities of harm – including unlicensed stem cells, chelation and hyperbaric oxygen – on the basis of muddle-headed beliefs entirely divorced from the scientific evidence. His office was raided by the FDA and Georgia Drugs and Narcotics Agency, he had already been caught out promoting pseudoscience in the autism omnibus trial and there was apparently an outstanding complaint against him by the parents of a child he had treated. Continue reading Family launching enquiry into mysterious death of anti-vaccine doctor

Autism is linked to gut problems (so sorry, Andy Wakefield)

Of all the persecuted Brave Maverick Doctors in WDDTY’s pantheon, none is more Brave or indeed more Maverick than Saint Andrew of Wakefraud.

Put simply, WDDTY desperately wants Wakefield to have been right, and will miss no opportunity to rewrite history in the service of this delusion.

As much as the medical community likes to discredit Andrew Wakefield for his theory about the MMR link to autism, research keeps supporting his central argument: autism is somehow related to the gut.

The medical community doesn’t like to discredit Wakefield. It doesn’t like discrediting anybody. Wakefield is discredited because he published fraudulent research with an undeclared conflict of interest, and because he conducted invasive tests on vulnerable children without proper ethical approval.

These are not small things. In any other doctor, they would cause WDDTY to lead the march with pitchforks and burning torches. Wakefield gets a free pass for these gross ethical violations only because his research serves the anti-vaccine agenda of WDDTY.

The latest has discovered that children with persistent gastro-intestinal (GI) symptoms are more than twice as likely to be autistic.

While this may be accurate, it is evidence of correlation not causation and it does not validate Wakefield’s fraudulent research, because Wakefield’s fraudulent research was designed to provide support for a legal action claiming that the MMR vaccine was the cause of autism, whereas the new research has nothing to do with vaccines.

The purported link between vaccines and autism – “the most damaging medical hoax of the last 100 years” – is refuted. This paper not only doesn’t overturn that, it doesn’t even address it.

It is extremely unlikely that any new research will prove a causal link between gut problems and autism, because autism has a strong genetic component, so gut problems are more likely to be co-morbid.

The risk dramatically increases in children who suffer from regular constipation, or food intolerance or diarrhea between the ages of six months and three years, say researchers from Columbia University’s Mailman School of Public Health.

Did you notice how this refutes the Wakefield claim that autism is caused by “measles enterocolitis” due to the MMR vaccination? The first MMR dose is at 12-15 months.

WDDTY “forgot” to mention that. They also “forgot” to mention that the paper has no mention of measles.

Although the connection is apparent, not all children with GI problems will go on to develop autism, any more than autistic children will necessarily have gut issues, cautions lead researcher Michaeline Bresnahan.

Well, duh. Most children will have at least brief periods of GI symptoms at some point, after all.

In this large prospective cohort, maternally reported GI symptoms are more common and more often persistent during the first 3 years of life in children with ASD than in children with [typical development] or [developmental delay].

No mention of a causal relationship, even speculatively.

Nonetheless, it was one of the key discoveries of Andrew Wakefield, who surmised that the MMR vaccine could be triggering the GI problems in the first place.

It wasn’t a “discovery” and this paper doesn’t say it’s a trigger.

Even Faux News did better, with the headline “frequent gastrointestinal issues may be early sign of autism”.

But you know WDDTY: any facts have to be beaten into compliance with their editorial agenda.

(Source: JAMA Psychiatry, 2015; doi: 10.1001/jamapsychiatry.2014.3034)

Note that any substantive finding of a causal link would not come form a psychiatry journal.

86 per cent of children with measles had been vaccinated

If there’s one thing guaranteed to fuel the build-up of spittle on the WDDTY editors’ computer screens, it’s positive coverage of vaccines. WDDTY is, to quote Ben GoldacreW, “viciously, viciously anti-vaccine” – and this is one of the things which elevates their tawdry health fraud advertorial to the status of public health menace.

The MMR vaccine is back in the news. Australian parents will lose their welfare benefits if they don’t vaccinate their children, while up to 86 per cent of children who caught measles during the ‘Disneyland outbreak’ in California last December were vaccinated, a new study has revealed.

Logical fallacy: non-sequiturW. The two are not connected, and not even in the same stories, in general. The 86% figure is mentioned only in order to make the evidence-based Australian policy look unreasonable.

WDDTY do cite a source, though returning to their former practice of obfuscating the reference to make it hard to track down. Why would they do that, I wonder?

Oh, wait:

An analysis of publicly available outbreak data suggests that substandard vaccination compliance is likely to blame for the recent measles outbreak linked to Disneyland in California, according to an article published online by JAMA Pediatrics.

I can see why they wouldn’t want you to find the original source.

Australian Prime Minister Tony Abbott has announced that parents who refuse to vaccinate their children will lose up to $11,000 of welfare benefits. Parents can opt out of vaccinations on medical or religious grounds, or because they are “conscientious objectors”.

But, from January next year, the conscientious objection opt-out will be removed in Abbott’s new “no jab, no pay” policy. Religious exemptions will also be tightened, and will apply only to religious bodies “approved by the government”.
The Australian government reckons that 39,000 families could lose their rights to welfare benefits.

Indeed. And the reason for the specific wording about religious bodies approved by the Government, is that Australian antivaxers invented their own church – the “Church of Conscious Living” – as a deliberate ploy to allow them to continue recklessly endangering the health of their children and those with whom they come into contact.

Their weaselly ploy has failed, and they are no doubt crying into their homeopathic beer about it.

US health authorities are also looking to tighten up on exemptions after the measles outbreak last December, in which around 140 children were infected. It is thought to have started at Disneyland in California.

It’s almost as if antivax sentiments evaporate when people are faced with the reality of preventable disease, isn’t it?

Which is of course why vaccines are not a hard sell with the postwar generation.

But a new study reckons that up to 86 per cent of the infected children had received all their MMR jabs. “Given the highly contagious nature of measles, vaccination rates of 96 per cent to 99 per cent are necessary to preserve herd immunity and prevent future outbreaks,” say the researchers from Massachusetts Institute of Technology.

When WDDTY reports the study as showing “up to” 86% of victims were vaccinated, they are being disingenuous. It actually says:

The authors estimate that measles, mumps and rubella (MMR) vaccination rates among the exposed population where secondary cases occurred might be as low as 50 percent and likely no higher than 86 percent. Because measles is highly contagious, vaccination rates of 96 percent to 99 percent are necessary to preserve herd immunity and to prevent future outbreaks, according to the study.

According to Wired,

The vast majority of the infected were unvaccinated against the disease, including kids who were too young for the shots and anti-vaxxers who chose against them. That’s how you get an outbreak. But six of the cases got their measles-mumps-rubella vaccine—the MMR shot—and still managed to get infected.

Wired also give a great description of how the Disneyland outbreak spread even to the immunised:

So how does that explain what happened in Disneyland? If you have a group of 1,000 people concentrated in a small space—like oh, say, hypothetically, an amusement park—about 90 percent of them will be vaccinated (hopefully). One person, maybe someone who contracted measles on a recent trip to the Philippines, moves around, spreading the virus. Measles is crazy contagious, so of the 100 people who aren’t vaccinated, about 90 will get infected. Then, of the 900 people who are vaccinated, 3 percent—27 people—get infected because they don’t have full immunity.

So WDDTY say “up to 86%” but other sources say closer to 10%. Why would WDDTY inflate the figure? We know why: to accurately report the case would require admitting that the MMR vaccine is around 97% effective, and that the figure they quoted was a discussion of the dangerously low level of vaccination that reduced herd immunity to the point that the outbreak could take hold.

And one thing WDDTY will never do is admit that the MMR vaccine works. Saint Andrew of Wakefraud would never forgive them.

 

WDDTY repeats hysterical anti-abortionist propaganda. Again.

WDDTY appear to be losing their marbles – perhaps they should nip down to the homeopath for some 30C Batshittium?

Back in October 2014 they ran “Autism ‘caused by MMR using human fetal cell lines’“, an entirely credulous repetition of a paper written and funded by a rabid anti-abortionist group, “showing” that foetal cell lines in MMR caused autism. Never mind that studies totalling over twenty million subjects fail to show any correlation, let alone cause, and please, oh please, don’t “follow the money” to the ideology-driven funding.

January 2015 contains the same story. It uses the same hyperbolic description – “major new study”, even though it’s no longer new and never was major. I tried to find out how often it had been cited, but drew a blank because the paper is not indexed on PubMed, and it’s not indexed on Google Scholar either, other than sowing up on “Liberation Chiropractic”.

Why is this “major new study” not showing up in the indexes?

The answer is right there in plain sight on the journal’s About page:

Manuscript Handling Fee
The manuscript handling fee for JPHE is $650 (USD).

Yup. JPHE is a predatory open access journal. The ideology-driven authors paid to have their ideology-driven conclusion-first research published. That’s why Orac found it so easy to shoot it full of holes.

The explosion in cases of autism has been caused by the introduction of human foetal cell lines in the manufacture of MMR (measles-mumps-rubella) vaccines, a major new study has concluded. Before 1987, when the vaccines were produced using animal cell lines, autism cases were relatively low. Today, it’s been estimated that one in 50 children has autism.

That would be significant if it were true. But the authors are Catholic fundamentalist anti-abortionists who run a group whose stated aim is to oppose the use of foetal cell lines, and it’s in a journal where you pay to get published, which is not indexed in PubMed. It is a junk study with massive and disqualifying conflicts of interest in a junk journal, and WDDTY have trotted it out not once but twice. Why?

Oh wait: Deisher has also spoken at Autism One, the anti-vax love-in where Wakefield is the saint du jour for every jour.

Stem cell researcher Theresa Deisher and others say that the correlation between the sudden explosion in autism cases and the introduction of the new MMR vaccines is too strong to ignore – although, as the old maxim goes, correlation doesn’t prove causation.

The “others” are all associated with the same fundamentalist group. There is literally no evidence at all of any independent support for this conjecture.

Meanwhile, even Catholics have a problem with this ideologically motivated tripe.

The “change point” – when the numbers of autism cases rose sharply – happened in the UK in 1987, just when the new MMR vaccine, using human foetal cells, was introduced. A similar correlation was seen at around the same time in Denmark, while the autism change point in the US was in 1980-1981, after the introduction of the new Meruvax and M-M-R II vaccines in 1979 – both of which used human foetal cells for the first time.

Has autism prevalence changed? Not in two decades it hasn’t. So what has changed?

In December 2014, Andrew Wakefield’s vexatious lawsuit against Fiona Godlee, the BMJ and Brian Deer ran out of time, after Wakefield failed to provide evidence for its continuation.

SO it’s likely that dear Lynne, bless her black antivaccinationist heart, is keeping the flame alive by promoting the only thing on her desk that had anything close to credulibility.

A happy new year to all our readers. May it be WDDTY’s last.

h/t @LennyLaw for the tipoff. Thanks!

WDDTY on: Andrew Wakefield

If there’s one figure the anti-vaccination movement idolises, it’s the struck-off former doctor and research fraudster Andrew Jeremy Wakefield. As a trailblazer for the anti-vaccination movement, Wakefield is widely identified as being responsible for current outbreaks of vaccine-preventable disease, causing serious harms and deaths.

This week, Wakefield’s frivolous case against the BMJ, editor Fiona Godlee and journalist Brian Deer, appears to have hit the buffers, joining his ill-fated 2005 suit against Channel 4 (which, it should be noted, was filed under the old and notoriously claimant-friendly British defamation laws). Continue reading WDDTY on: Andrew Wakefield

Doctors who question vaccination are being ‘forced out of medicine’

Thanks to the editors of WDDTY for a rare bit of good news:

English doctors who may be ambivalent about vaccines are being weeded out of the profession by the ‘revalidation’ process, where they have to renew their licence to practice.

Being “ambivalent about vaccines” is a great litmus test I agree. Any doctor who can read the literature and still remain “ambivalent” about one of the most important public health measures clearly has seriously deficient judgment.

Around 8,500 doctors have already left the profession after failing to meet the requirements of the process, and this includes doctors specialising in environmental medicine and others who may hold any ‘alternative’ views.

Again, great news. If you haven’t heard of environmental medicine, read this article in Science Based Medicine and this on Quackwatch. In the UK it was formerly branded clinical ecology and has nothing to do with the reality-based practice of environmental medicineW.

Remember Minchin’s Law: alternative medicine, by definition, either hasn’t been proven to work, or has been proven not to work. Doctors who employ alternative medicine in clinical practice will definitely need watching and those who advocate for it are often engaged in pathological scienceW at patients’ expense.

In particular, if the execrable Saatchi Bill is passed, it will be extremely important to weed out the mavericks because they will be protected from the consequences of capricious and ill-judged actions.

Under the requirements, doctors must “protect your patients, your colleagues and yourself by being vaccinated against common serious communicable diseases where vaccines are available.” Doctors who are unable to demonstrate that they have been fully vaccinated are being forced to leave medicine.

Absolutely reasonable. In daily practice doctors are very likely to meet both immunocompromised patients and those suffering from vaccine-preventable disease, especially if some of their patients read vile anti-vaccine propaganda sheets like WDDTY. It’s vitally important that doctors do not become a vector for these diseases, and no responsible doctor would wish to take the risk.

The important thing to remember is that in the well-documented absence of any rational grounds for refusal of vaccination, a doctor who refuses is placing ideology above evidence. Placing evidence above ideology is one of the signatures of modern medical practice. Sir Lancelot Spratt is no more, and good riddance to him.

One doctor, who wishes to remain anonymous, told WDDTY: “I fear this will drive many doctors who are not sure about the benefits of vaccines undercover or out of the profession. This will also not serve patients’ rights to a balanced opinion of vaccines, as the doctor, whatever their opinion, will be now forced to be only positive about vaccines if they want to keep their licence to practice as a doctor and keep working.”

Anonymous sources are so convenient, aren’t they? One must assume that if this is not Jayne Donegan, as she would very likely have kicked up a stink publicly.

For the avoidance of doubt, a “balanced view” on vaccines is that they are very safe and prevent serious diseases. Adverse effects are rare, almost invariably minor, and even at their worst, are significantly less than the worst case outcomes for the diseases they prevent. More to the point, doctors are completely open about the real (tiny) risks of vaccines, contrary to antivaxers’ claims.

To assert that a balanced view falls somewhere between the scientific consensus as presented by responsible doctors, and the alarmist bullshit presented by antivaxers, is the fallacy of false balance. The scientific consensus view incorporates all known evidence weighted according to quality. You can’t “balance” that by also presenting long-refuted antivax tropes.

“What Doctors Don’t Tell You” – Dangerous advice

Reblogged from Swift at the James Randi Educational Foundation

If you want an alternative to reputable health magazines, look no further than What Doctors Dont Tell You (WDDTY) – the winner, once again, thanks to assiduous astroturfing, of a “people’s choice” award for most popular website in the Health category.

Continue reading “What Doctors Don’t Tell You” – Dangerous advice

Vaccines won’t protect our children, say 74 per cent of parents

The stupid. It burns.

WDDTY’s story “vaccines won’t protect our children, say 74 per cent of parents” covers a publication which shows that 74 per cent of parents understand that antivaxers are a public health risk.

Yes, that’s right: McTaggart says that anybody who understands the dangers of unvaccinated children, believes that vaccines won’t protect their kids.

Most parents don’t believe in the protective effects of vaccinations.

Why do you think that might be? Anything to do with the antivaccine lobby? Including the “viciously, viciously anti-vaccine” Lynne McTaggart?

According to one survey, 74 per cent of American parents said they would remove their vaccinated children from a daycare centre if there were any children attending who weren’t up-to-date with the vaccine schedule.

Very sensible – no vaccine is 100% effective and unvaccinated children are one reason why the US is currently seeing outbreaks of measles and pertussis, both of which had been virtually eliminated prior to the Wakefield farrago.

Although it’s mandatory for every child attending a daycare centre in the US to be vaccinated with the MMR and other childhood vaccines, they do not have to have received all the vaccines.

Thanks to assiduous lobbying by antivaxers, yes. You must be so proud.

In a US survey carried out by the University of Michigan, most parents believe that the centres should police vaccination schedules, and 74 per cent said they would consider boycotting a centre if they knew that as many as one in four children was not fully up-to-date with vaccinations.

It’s almost as if there is a resurgence of vaccine preventable disease, isn’t it?

The questions didn’t mention children who were still unvaccinated.

On the grounds that an unvaccinated child is, by definition, either too young to have been vaccinated, so up to date, or not fully up-to-date with their vaccines. How is this not obvious?

Just 10 per cent of parents were relaxed about the idea of children who weren’t fully vaccinated.

Still far too many. But the public education campaigns should fix this in time, as long as WDDTY and their antivax fellow-travellers never mention vaccines ever again.

All of which beggars the question: isn’t your child supposed to be protected anyway?

No, Lynne. Your story beggars belief, but the report does not beg the question, because anybody who is even slightly educated about the vaccine issue recognises precisely what it means: three out of four parents think you and your ilk are a public health danger.

The other one out of four need to wise up.

Update

@Zeno001 reminds me that there are two messages here. The first is the bald assumption of the anti-vax trope “if vaccines work, why are we a threat?”, which is based on the false assertion that medicine claims all vaccines to confer 100% immunity to the relevant disease. This is, of course, tosh, and is one reason why herd immunity is so important.

The other message is that large numbers of people – most, in fact – are not taken in by the anti-vax bullshit. This si great news for the reality-based community and it’s just a shame that it has taken deaths and serious harm in outbreaks of preventable disease to bring home to people why vaccination is important. We’ll never kill the zombie memes set loose by Wakefraud, but we can isolate them in small pools until they die out naturally. A well informed population is effectively vaccinated against bullshit, it’s not 100% effective but a high enough immunisation rate prevents outbreaks.