I have a Facebook acquaintance who is rabidly anti-vax. While I’d like to unfriend her, I’d also like to sign off by giving her a few quick whacks with the clue stick first. Trouble is, I don’t know a great deal about anti-vax arguments and my google-fu is weak.
Obviously, vaccines work. Smallpox plagued mankind for 10,000 years but it only took 20 years of vaccination to wipe it out for good.
My question concerns herd immunity. I’ve heard it said that vaccination rates must stay above 95% otherwise herd immunity is compromised. My question is, if one has been vaccinated, what does it matter how many other people have been vaccinated? If I were the only person in Britain to be vaccinated against measles, mumps, and rubella, surely I would be safe. Everyone else around me might get sick, but if I’ve had the vaccine, surely that’s me taken care of.
Basically, what I’m trying to ask is why should the vaccinated fear the unvaccinated? What does it matter to those who are protected whether 5% or 50% of their fellow citizens refuse the jab? How can a person’s beefed-up immunity be compromised by the lack of same in his neighbours?
Umm… because they’re not sociopaths and don’t want to see people suffer?
A. Some people cannot be vaccinated, due to immune deficiency or other conditions. Babies aren’t fully vaccinated at birth.
B. Vaccines are close to, but not 100% effective.
C. Children don’t deserve to suffer/die just for being born to moronic antivax parents.
I’m not sure how strong your google fu has to be for wikipedia - which by the way pretty clearly indicates a threshold of something a bit lower than 95% for most common vaccines.
Oh, and apologies, but whenever I hear the phrase herd immunity I can’t help myself.
Herd immunity benefits the unvaccinated. If everyone but one person is vaccinated, that that one person doesn’t have to worry. But if more than 5% are unvaccinated, then the disease will continue to find hosts and live. Which means the disease is never truly eradicated and so the next generation will need to be vaccinated also.
Vaccines are usually around 90-99% effective. This leaves alot of people vulnerable. For instance say there is a population that is 80% vaccinated against a disease that affects 50% of the unvaccinated and 5% of the vaccinated. If there is an outbreak of the disease then 44% of people affected will have been vaccinated.
However if herd immunity threshold had been crossed, no one who was vaccinated would have gotten the disease.
In terms of percentages anti-vaccination people don’t affect other’s odds that much, but in terms of absolute numbers of people who will get sick it is a big deal.
Ah, thank you, puddleglum. If I understand correctly, then what you’re saying is that even vaccinated people might worry that they are among the small minority for whom the vaccine doesn’t work. But if they’re above the 95%, then they don’t even need to worry about that.
Herd immunity rates differ based on the disease. Slide 17 on this PDF from the CDC shows that some diseases may have herd immunity vaccination rate requirements as low as 75%. Obviously, higher vaccination rates are always better.
I’ve also heard that the effictiveness of some vaccines fades with the decades. They’re recommending that adults have a whooping cough booster, for example, since it’s started to spread again.
To add an anecdote to the data, I’ve had 3 rubella shots and tests still show that I have no immunity. (Testing for rubella immunity is part of the standard prenatal package.) Either the vaccine doesn’t work for me, or I’m immune but it doesn’t show when tested.
But it’s not just the resurgence of pertussis. The new acellular formulation for the pertussis vaccine is slightly less effective than the old one (inactivated cells). But it produces fewer side effects.
It’s a bit of a trade-off, which wouldn’t be as much an issue if kids were properly vaccinated and herd immunity was in play.
Simple explanation: the greater the degree of vaccine protection in the “herd”, the less chance disease has to spread, benefiting both the unvaccinated (including those who are too young or immunosuppressed to get the vaccine) and the minority of vaccinated persons in whom the injection didn’t “take”.
The degree of “herd immunity” or percent vacinated depends on how easily the disease spreads. I.e. if X percent are susceptible, then what are the odds that they will run across another person who is already infected, and then pick up the disease.
The suggestion is that there is a tipping point, where if X is low then odds of a case spreading are low; if X psses a certain threshhold, the odds climb quickly.
When the method of immunization was “you’ve already suffered through the disease” then plagues came in waves. Everyone got it. Some (most) survived. Relative immunity was high, so isolated cases went nowhere. After a few decades, immunity percent dropped - most people were born after the epidemic. At a certain point, immunity was so low that a new case would trigger another wide epidemic.
Vaccines are meant to keep the immunity level high. Thus, the odds of one person who was not immune, running into another who had the disease, was close to zero.
Think of skipping vaccines as analogous to skipping a line-up for a bus or theatre. If everyone else stays in line, the one selfish person can jump the queue and not have to wait. If too many do, then the line dissolves into a shoving match and there’s no advantage.
Herd immunity protects more than the anti-vaccination crowd*. There are millions of people, for instance, who are allergic to one or more vaccines, as well as people with compromised immune systems that couldn’t handle the medicine, etc.
When perfectly healthy people refuse vaccination solely because of pseudoscience, they put those who legitimately cannot receive the vaccine at risk.
Additionally, some vaccines wear off, and people are sloppy about boosters. Elective non-compliance with vaccinations elevates the risk for this group of previously vaccinated people. Additionally, those who catch these preventable diseases increase medical costs, and take an emotional toll on those who watch their senseless suffering.
(*I don’t consider bona fide religious objections to fall under the “anti-vaccination crowd”)
Just want to chime in here that there are a huge number of folks who aren’t anti-vax for pseudoscience reasons (like it causes autism), but are anti-vax because of conspiracy reasons (governments use vaccinations to experiment on us, mind control us, etc).
Sorry for the thread derailment. But yeah, herd immunity helps protect those idiots.
A more scientific reason is that they may not stay protected for long. If the virus is able to survive long enough in a large un-vaccinated population, antigenic drift can occur. The virus mutates to a point where the vacine is no longer effective.
For example, I’m a physician and a scientist, and I’ve spent a significant amount of time pointing out the value of vaccination. I have a very close adult relative who has an anaphylactic allergy to egg. As a result, flu vaccines are contraindicated, so she relies on herd immunity - aka - everybody else getting a vaccine, so that she doesn’t get exposed.