I’m Karie Youngdahl, the director of historyofvaccines.org, an award-winning website from The College of Physicians of Philadelphia about vaccine history. Our aim is to explore the role of vaccines in human health, both historically and in the present. Given the current US measles outbreaks, I’ve been getting lots of calls from reporters and from the general public about vaccines, vaccine history, and measles history. AMA!

My proof: Here I am with a wax model of an arm with smallpox. This is in our Mütter Museum. Smallpox is the only human disease to have been eradicated (through vaccines!).

Victoria from Reddit is helping me today. Michelle Sipics, our former content developer, is here to help answer questions, too.

Thanks, everyone, for all the great questions. Signing off for now. You can always Tweet questions to @historyvaccines. I'll try to keep checking in throughout the rest of the day! You've been amazing!

Comments: 380 • Responses: 53  • Date: 

differencemachine60 karma

do you believe that vaccinations cause altruism?

historyofvaccines42 karma

We believe that you are awesome.

restatic18 karma


historyofvaccines34 karma

People are concerned about the measles outbreak. I think it's understandable because measles has become a thing of the past here in the US. Plus the Disneyland angle has made it more attention-getting.

mymassive16 karma

Why is the shingles vaccine not allowed for people under the age of 50? What is the science behind that? (I had shingles when I was 27 and I wish there was something I could've done to prevent it)

historyofvaccines13 karma

It's about when the greatest risk of shingles is: after age 60. So we have to balance length of effectiveness against time of greatest vulnerability. Sorry about the shingles episode: it sounds horrible.

historyofvaccines10 karma

(from Michelle) -- I also had shingles at a young age (about 30) and I sympathize. I really wish I could have been vaccinated against it.

notsomuchreally15 karma


historyofvaccines34 karma

The drop was the live oral vaccine, developed by Sabin. The shot is the inactivated vaccine, developed by Salk. It's given via injection. The live vaccine is more effective but has a higher risk of side effects. So in countries like the US where polio is not circulating, the inactivated vaccine is used instead.

historyofvaccines12 karma

Here's a link describing how OPV was phased out and IPV phased in in the US http://www.historyofvaccines.org/content/timelines/diseases-and-vaccines#EVT_100337

______DEADPOOL______8 karma

What kind of side effects? Also: is the live vaccine cheaper? I've seen those donation solicitation for 3rd world country vaccines and they're like, what, a buck a kid?

historyofvaccines15 karma

Yes, the live vaccine is cheaper not only to manufacture but because it's easier to give. The main side effect is that the vaccine virus can revert in very rare cases to a virulent form and cause polio.

Pka15215 karma

What's your worst fear?

historyofvaccines110 karma

That the new Star Wars movies will have a character worse than Jar Jar Binks.

tommychains12 karma

If there was one thing you could say to convince anti-vaccination advocates to change their mind, what would you tell them?

historyofvaccines37 karma

I would say that I got my own kids fully vaccinated. And I've spent six full years working on vaccines: that's how important I think it is.

hillcountrygirl10 karma

Why don't we receive the package insert when getting a vaccine similar to the sheet you get with a prescription? Are the trials for vaccines as strict as for new drugs?

historyofvaccines20 karma

We have an article on vaccine development, testing and regulation that may interest you. In general, vaccines are even more thoroughly tested than non-vaccine drugs because the number of human subjects in vaccine clinical trials is usually greater.


There recently was a measles outbreak thanks to antivaxxers. What do you predict the next antivaxxer-related outbreak will be?

historyofvaccines20 karma

We're having ongoing pertussis outbreaks here in the US. But the issue isn't just non-vaccination -- we need a more effective vaccine. Also note the recent mumps outbreak in the NHL -- again, we need a more effective vaccine for that, too.

transemacabre8 karma

What do you think of designing bacteriaphages, viruses that attack and destroy bacteria, to help eradicate bacteria-caused diseases?

historyofvaccines14 karma

They aren't used in the US so I don't feel comfortable saying too much about them, but it would be interesting to see more research.

FlamingWings7 karma

How do you feel about anti-vaxxers?

historyofvaccines21 karma

Personally or professionally? haha

FlamingWings13 karma

both point of views actually.

historyofvaccines28 karma

Professionally, I think it's interesting that many of the same arguments (in general) have been used across time and that they are very effective at getting their message heard (again, this has historical precedent) We have an article about this here. Personally I have met some very nice anti-vaxxers but try to avoid discussing vaccination directly with them because it usually does not end well.

transemacabre6 karma

Do you think you will see a viable HIV/AIDS vaccine in your lifetime?

historyofvaccines21 karma

I'm going to say yes, because the RV144 trial had some success. I want to be hopeful.

______DEADPOOL______6 karma

Since the eradication of smallpox, does the virus or whatever it was still being kept as sample or biological weapons somewhere? What are the risk of someone encountering smallpox in the wild from other animals or whatnot and getting smallpox again? And reintroducing it back to society?

historyofvaccines17 karma

Smallpox lives in a few labs (and maybe more places we don't know about). There is no animal reservoir so there is no risk from wild animals. There have been concerns raised about smallpox used as a bioweapon and so there's lots of smallpox vaccine stockpiled in the US

______DEADPOOL______5 karma

If someone manage to use it as bioweapon, what kind of damage are we looking at?

historyofvaccines17 karma

Smallpox had a 30-40% case fatality rate naturally. If someone was to use it as a bioweapon, they would likely try to make it more transmissible and/or deadly...so severe damage.

______DEADPOOL______5 karma

How does one make it more transmissible/deadly?

historyofvaccines32 karma

I could tell you, but I'd have to kill you.

2noame6 karma

Have you happened across this recently published article yet about the possibility of using a social vaccine to vaccinate against poverty as we used the smallpox vaccine to eliminate smallpox?

Do you believe we could see the same incredible potential savings through reducing poverty as we have in reducing diseases like smallpox, polio, measles, etc?

historyofvaccines6 karma

Our focus is obviously on human disease, but equally obviously we think prevention works pretty well. So while this is a little beyond our scope of expertise, we think it's a reasonable approach.

sharpy1110 karma


historyofvaccines13 karma

No. Do you?

mikecandigit5 karma

Hi Ben's mom!

Did Doug ever get his fitbit working?

historyofvaccines4 karma

Hi Mike! Doug loves his FitBit and checks his progress constantly. How's your custom beard oil blend, and is Ben caught up in his classes?

mikecandigit4 karma

Ben is great! He took a class with a professor I recommended, so I take full credit for his success. I actually haven't bought any beard oil yet, I have to decide if I really want to keep growing my beard for that long. I'll keep you posted! Casey says hi too!

As long as I'm here I figure I should ask some question about vaccines, but unfortunately I can't think of one... I guess my question will be: What is the most common argument you have to combat when talking to anti-vaxxers? I feel like the rumor that vaccines cause autism has been largely debunked lately, but is there anything else anti-vaxxers try to argue?

historyofvaccines6 karma

Sure, they have lots of arguments and it's kind of like playing Whac-a-Mole to combat them. I really think the best arguments for vaccines are in the excellent, large-scale studies that are constantly being done on vaccine safety.

Pka1525 karma

Thoughts on Jenny McCarthy ?

hillcountrygirl5 karma

If Hep B is generally spread through sex and drug use, why do we give it to 2 day old babies?

historyofvaccines25 karma

Hepatitis B can be spread through sex and drug use, but also during birth (an infected mother can give it to her child), or through contact with bodily fluids or open wounds from someone with the disease. There may be a very small chance that a newborn will be exposed to the virus, but here's the key point: the younger you are when infected with Hepatitis B, the more likely it is to become chronic. Among infants who are infected, about 90% will develop a chronic Hepatitis B infection. That's why the vaccine is given so early.

goatcoat5 karma

What is the exact function of mercury in mercury-containing vaccines?

Please be as technical as possible with your answer. We're all nerds and can google the terms we don't understand.

historyofvaccines9 karma

Thimerosal: used to prevent life threatening contamination of vaccines, particularly in multi-dose vials that get used for many vaccinees. It's used mainly in multi-dose influenza vaccines now.

sethfm4 karma

Re Gates and vaccines: is there less government money going into vaccine research today, creating a need for more philanthropy? Or is philanthropy supplementing aggressive funding of research?

historyofvaccines9 karma

The philanthropy right now is driving increased access to vaccines, not really innovation. Though Gates and others are spending on innovation, too

hillcountrygirl4 karma

Who decides which vaccines our kids should get and do they have ties to pharmaceutical companies?

historyofvaccines15 karma

The Advisory Committee on Immunization Practices decides. Some of them but certainly not all of them have ties to pharma. We have to accept that these are the people who have expertise in the area.

katrinald3 karma

I believe in vaccinations wholeheartedly. I have no children but I worry about adults, and maybe selfishly, myself. I had to be revaccinated for MMR before attending University and I contracted whooping cough a few years ago and was promptly given a vaccination afterward. Even though I was given all vaccinations as a baby, there seem to be things that I can still catch as an adult. What other diseases am I or other vaccinated adults prone to getting because of this anti-vaxx movement?

historyofvaccines5 karma

For adults, the ones we'd be most at risk for are pertussis, influenza, hpv, etc. But I don't think we should blame all of the susceptibility to the anti-vax movement. There's more nuance involved, such as vaccine effectiveness and people's access to vaccines that prevents them or their kids from getting vaccinated.

sethfm3 karma

How was the measles vaccine originally developed?

historyofvaccines5 karma

It started when Peebles isolated the measles virus http://www.historyofvaccines.org/content/timelines/diseases-and-vaccines#EVT_100511. Enders's lab then attenuated (weakened) the virus. It was licensed in 1963

823642 karma

Why study vaccines?

What advancements are anticipated, in the foreseeable future?

What are the highest priorities? (And why?)

What notable failures, in the history of vaccines, are there?

How have vaccines changed, over time?

historyofvaccines8 karma

One notable failure was that of the Lyme disease vaccine. We discuss that here. It was a matter of perceived side effects. But it also had short-lived immunity.

Vaccines have gotten less complex in terms of antigens -- there are many fewer antigens in vaccines now. The total load of immunogens in vaccines is now under 200 different types. It used to be more than 3000. See this info **edited for links

lyrelyrebird1 karma

Are they still working on the Lyme Disease vaccine, or because of this failure they have stopped?

historyofvaccines6 karma

Several new vaccines are in development. This is another one that may become more important as a result of climate change, as the ticks that carry lyme spread into new areas.

nickm94792 karma

Why is there such a controversial anti-vax movement?

historyofvaccines16 karma

Again, it's important to point out that most people do acknowledge the value of vaccines, and do vaccinate their kids. Fortunately for all of us, it's a very small percentage of people who actually refuse vaccination. (Of course, as we're seeing with measles, if that percentage gets high enough the diseases are ready to take advantage and make a comeback.)

But it's easy to understand why people can be uncomfortable about the idea of a vaccine -- you're injecting a piece of a virus or bacterium into yourself! Sometimes it's a piece of a bacterium's outer shell; sometimes it's an inactivated version of a virus; sometimes it's a live form of a virus that's been altered so that it can't make you sick. But when you learn about how all of these vaccines are made, they stop being scary. In fact, vaccine science is pretty darn cool. We have articles about how vaccines are made and different types of vaccines on our website!

MagmaiKH3 karma

Has it been confirmed that it's classic measles and not a new strain?

historyofvaccines5 karma

CDC has characterized many cases in this outbreak as related to the measles virus that's circulating in the Philippines see this link

citatser-5 karma

Do you think it's fair to deny someone an education because their parents won't agree to vaccinate their kids against every disease mandated by gov't?

historyofvaccines26 karma

Some states have ways to exempt kids, if parents don't want them to get vaccines. Or, you can try to find a private school that doesn't require vaccines. I don't think it's fair for immunocompromised kids to be potentially exposed at school to diseases we can easily prevent.

tommychains2 karma

What disease do you believe in your professional opinion will be eradicated next?

historyofvaccines11 karma

Guinea worm! Go Jimmy Carter! We're almost there. (no vaccines though). I hope polio will be the next vaccine preventable disease eradicated

PJinPA3 karma

In addition to the amazing work on eradicating guinea worm, which current vaccine research or clinical trials are you most optimistic about?

historyofvaccines10 karma

I think it's wonderful that people are working on vaccines against chikungunya and dengue, because the disease burden with those is already so high and is likely to grow.

TheTimelordTrekkie2 karma

Do you worry that some diseases will mutate and current vaccines will be ineffective?

historyofvaccines7 karma

Not really. I'm worried more about emerging diseases we don't have vaccines for

huskywench2 karma

Why do boys need the HPV vaccine when it's a cervical cancer vaccine?

historyofvaccines15 karma

Several reasons: it prevents spread of HPV to girls, and so it can protect them, too, and reduce the burden of the disease across the population. Second, it prevents them from getting HPV infections that can lead to anal, penile, and throat cancers. Plus, warts

______DEADPOOL______2 karma

The other day Bill Gates was here about his 15 yr bet and one of them was that we'd get rid of four diseases by 2030 partly by vaccines. How realistic is this goal? Especially with antivaxxers around.

And what was vaccination like in ancient times?

historyofvaccines12 karma

We think it's important to point out that the vast majority of people do appreciate the value of vaccines and do vaccinate their kids. Of course there are challenges, but when it comes to eradication, the biggest challenges are more to do with delivery vaccines to remote parts of the world and paying for treatment. Proper storage (temperature control) is also a major concern, and having trained vaccinators. I think it's going to be challenging. If we take the lesson of smallpox into account we see that it took many many more years than anticipated to eradicate.

______DEADPOOL______2 karma

What kind of training does vaccinators get? It seems like an easy poke-the-needle job that even drug addicts can figure out on their own. Especially mouth drop type vaccination.

historyofvaccines6 karma

Community health workers often work on vaccination campaigns in developing countries. They get training, though.

historyofvaccines3 karma

As for ancient times, vaccination really started with attempts to protect people against smallpox. You can read all about it on our smallpox timeline, here: [http://www.historyofvaccines.org/content/timelines/smallpox]

ColdplayParadise2 karma

This doesn't have to do with health, but, your last name... what origin does it have? Is it maybe of Scandinavian descent?

historyofvaccines6 karma

I come from happy Swedes

push-over2 karma

There has been talk about a cancer vaccine being developed and with good results. Is this really possible and will we see it in the near future?

Just googled and found out it's called Telovac!

historyofvaccines4 karma

We have two cancer vaccines now -- hepB (can prevent liver cancer) and HPV (prevents a variety of cancers). Yes, I think we'll have more cancer vaccines in future, and vaccines for immunotherapy for cancer too. We discuss this here http://www.historyofvaccines.org/content/articles/cancer-vaccines-and-immunotherapy

mylittleporkbun2 karma

Do you get a lot of fan mail? Also, what's the address?

historyofvaccines4 karma

We both get a lot of mail (and tweets). We're a lot of fun at parties.

Neednothing1 karma

What is/might be the most effective way of reaching out to those who do not vaccinate?

historyofvaccines2 karma

I think we should think of people's attitudes on a continuum...with rejectors on one side and automatic acceptors on the other. There's a lot of room in the middle. For those people, strong doctor recommendation is associated with vaccine acceptance. Many researchers are also investigating effective provider communication styles (here I'm thinking of Julie Leask in Australia) and how those styles can lead to vaccine acceptance

nanyanwu1 karma

Did Dr. Salk found a cure for polio?

historyofvaccines4 karma

No, he developed a vaccine that was licensed in 1955.

lyrelyrebird1 karma

What do you think about the HPV vaccine? I know it had some controversy when it came out about the side effects (those I knew, including myself, who got vaxxed didn't have any problems). But I assume now it is safer, and looks like its on the vax schedule.

historyofvaccines4 karma

I made sure my kids (boy and girl) got it (and had no side effects). It has a good safety profile and it is very effective at preventing vaccine-type hpv infections.

______DEADPOOL______1 karma

Was measles really that bad as to senounce anti vaxxers? I remember the time when parents would send their kids to contract measles in other kids home so they'd get immunity. Wouldn't most adults have this immunity now?

Especially since most kids are vaccinated and adults went through all that, why would the measles oubreak be a bad thing?


historyofvaccines15 karma

Measles can be mild. It can also have serious side effects. In France etween 2008 and 2011 almost 5000 pts were hospitalized (more than 1000 for severe pneumonia) and 10 died. More than 80% were completely unvaccinated. Encephalitis can result too.

edited to clarify that this was in France

MagmaiKH0 karma

What is the worst vaccine disaster in history?

e.g. Something along the lines of the fungal contamination of the steroid shots in 2013.

historyofvaccines1 karma

I would say the 1929 Lubeck disaster. 72 babies died from BCG (TB vaccine) that was contaminated with virulent live human TB bacilli