Tag: herd immunity

What Happens When You Research the Disease?

We know how anti-vaccine folks think.

Anti-vaccine math…

And now we know how they do their research

How Anti-Vaccine Folks Research Disease

If you’re like me, you are probably wondering why they picked 2016 as the year to research.

Why look just at 2016?

And, there you see it.

In the past 6 years, 2016 was the year with the fewest cases of measles. Why not choose 2017 or 2018 to do their research?

But let’s look at 2016, even though the information isn’t complete:

  • 86 cases
  • cases in 19 states, including Alabama, Arizona, California, Colorado, Connecticut, Florida, Georgia, Hawaii, Illinois, Massachusetts, Michigan, Minnesota, New York, North Carolina, Oregon, Tennessee, Texas, and Utah
  • a large outbreak in Arizona (31 cases) linked to a private detention center and all that is known is that 7 of 9 staff members who got measles had received at least one dose of MMR, and 3 had received their dose very recently
  • a large outbreak in Shelby County, Tennessee, at least 7 cases, including 6 unvaccinated and one partially vaccinated child
  • a large measles outbreak (17 cases) in Los Angeles County and Santa Barbara County that was linked to the Los Angeles Orthodox Jewish community
  • two cases in Colorado, including an unvaccinated toddler and an unvaccinated adult – outbreaks which cost at least $68,192 to control

And of th cases in 2016, it seems that just 16% were vaccinated.

What about the claim that 26% were vaccinated?

That wasn’t 26% of the total number of cases, but rather 26% of the cases among US residents.

So if you do the math, that’s just 14 cases that were vaccinated, and out of 86 cases, that’s really just 16%. And a lot of those cases are skewed by the one outbreak at the detention center, in which they may have only received one dose of MMR and nearly half may have gotten vaccinated after the caught had already started!

What about the claim that “the odds of dying from the measles are like 0.00000013%” using numbers “before the vaccine was introduced in 1963?”

“Before a vaccine became available in 1963, measles was a rite of passage among American children. A red rash would spread over their bodies. They would develop a high fever. Severe cases could cause blindness or brain damage, or even death.”

CDC says measles almost eliminated in U.S.

In the pre-vaccine era, your odds of getting measles were very high. Remember, everyone eventually got measles.

And looking at statistics of reported measles cases and reported measles deaths, we know that death occurred in about 1 to 3 in every 1,000 reported cases.

So everyone got measles, but not everyone survived having measles.

Even if you use a more liberal count of 1 death in 10,000 cases, when all kids get measles, that’s a lot of deaths. Remember, about 450 people used to die with measles each year.

What about your odds of dying with measles now?

If you are fully vaccinated, then they are extremely low.

They are pretty low if you are unvaccinated too, in most cases, because you are benefiting from herd immunity and the fact that most folks around you are vaccinated, reducing your risk of being exposed to measles. Still, the risk is much higher than most anti-vaccine folks expect, because they often make the mistake of using the entire population of the United States in their calculations. They should instead just use the folks who are unvaccinated and susceptible, a much smaller number.

Want to increase your risk?

  • travel out of the country
  • hang out in a cluster with other unvaccinated people
  • stay unvaccinated

The odds aren’t in your favor to avoid measles if you are unvaccinated. Eventually, your luck might run out.

Starting to see the mistakes anti-vaccine folks make when they say they have done their research?

“How do they know how many people would have gotten measles and how many of them would have died?!?”

It’s not rocket science.

It’s epidemiology.

“We constructed a state-space model with population and immunisation coverage estimates and reported surveillance data to estimate annual national measles cases, distributed across age classes. We estimated deaths by applying age-specific and country-specific case-fatality ratios to estimated cases in each age-country class.”

Simons et al on Assessment of the 2010 global measles mortality reduction goal: results from a model of surveillance data.

Unfortunately, after years of improvements, measles deaths increased in 2017. And they will continue to increase, as our risk of getting measles continues to increase if folks don’t get vaccinated and protected.

Lastly, why does it “sound like millions of people would have died without the measles vaccine?”

Maybe because millions of people died in previous years, before they were vaccinated and protected.

Indeed, do your research, but you will find that vaccine-preventable diseases aren’t as mild as anti-vaccine folks believe. That’s why it is important to get vaccinated and protected.

More on Researching Vaccine-Preventable Disease

How Often Should You Do Vaccine Titer Testing?

We sometimes hear about folks doing vaccine titer testing.

A vaccine titer is a blood test that can determine whether or not you are immune to a disease after you get a vaccine.

While that sounds good, after all, why not check and be sure, it has downsides. Chief among them is that the results aren’t always accurate.

That’s right. You can sometimes have a negative titer test, but still be immune because of memory B cells and the anamnestic response.

How Often Should You Do Vaccine Titer Testing?

So how often should you do vaccine titer testing?

It depends, but most folks might never have it done!

Why not?

Vaccines work very well, so you would typically not need to routinely check and confirm that you are immune after being vaccinated. And, this is also important, the vaccine titer tests don’t always work that well, titer testing isn’t available for all vaccines (you can’t do titer testing for Hib and pertussis), and the testing can be expensive.

So we usually just do the testing (a quantitative titer) for folks that are in high risk situations, including:

  • pregnancy – rubella titer only (HBsAg is also done, but that’s not a vaccine titer test, but rather to see if you are chronically infected with hepatitis B)
  • healthcare workers – anti-HBs (antibody to the hepatitis B surface antigen to confirm immunity after being vaccinated)
  • students in nursing school and medical school, etc. – anti-HBs
  • children and adults exposed in an outbreakmeasles, chicken pox, mumps, etc., but only if we are unsure if they were previously vaccinated and protected
  • after a needlestick injury, etc. – to confirm immunity to hepatitis B
  • babies born to a mother with hepatitis B – to confirm that their hepatitis B vaccine worked

Vaccine titer testing might also be done for:

  • internationally adopted children – to confirm that they are immune if we unsure about all of the vaccines the child got in other countries
  • children and adults with lost vaccine records – to confirm that they are immune, since we are unsure about all of the vaccines they got
  • evaluation of children and adults with immune system problems – to help identify what immune system problems they might have – typically involves checking pneumococcal titers, giving Prevnar, and then checking pneumococcal titers again
  • people at continuous or frequent risk for rabies – rabies titer testing every 6 months to 2 years
  • patients with inflammatory bowel disease, before starting immunosuppressive therapy – hepatitis A and hepatitis B titers, as they might be at increased risk for hepatitis

While checking titers is easy, it is sometimes harder to know what to do with the results you get.

Of all of these different titers, only one tells you that you are immune due to vaccination.
Of all of these different titers, only one tells you that you are immune due to vaccination.

It is especially important to know that:

  • most people don’t need to have their titers checked routinely if they are not in one of the high-risk groups noted above
  • it isn’t practical to get titers tested as a method of potentially skipping one or more doses of your child’s vaccines, after all, if the titer is negative, then you are still going to have to get vaccinated
  • a healthcare provider with a negative measles titer after two doses of the MMR vaccine does not need another dose of vaccine
  • a healthcare provider who has anti-HBs <10 mIU/mL (negative titer) after three doses of the hepatitis B vaccine should get another dose of vaccine and repeat testing in 1 to 2 months – if still <10 mIU/mL, they should then get two more doses of hepatitis B vaccine (for a total of 6 doses) and repeat testing. If still negative, these documented nonresponders will need HBIG as post-exposure prophylaxis for any future hepatitis B exposures, but no further doses of hepatitis B vaccine.
  • vaccinated women of childbearing age who have received one or two doses of rubella-containing vaccine and have rubella serum IgG levels that is not clearly positive should be administered one additional dose of MMR vaccine, with a maximum of three doses, and should not be tested again
  • postvaccination titer testing is not recommended after the chicken pox vaccine
  • in addition to not being able to test titers for pertussis and Hib immunity, it is becoming difficult to test poliovirus type 2 titers, as the test uses a live virus that isn’t routinely available anymore (type 2 polio has been eradicated)

Still think you need vaccine titer testing?

More on Vaccine Titer Testing

Can I Get a Second Flu Shot for Extra Protection?

If one flu shot is good, wouldn’t two be better?

Can I Get a Second Flu Shot for Extra Protection?

Some people do get a second flu shot.

In fact, all kids eight years and younger, if it is their first time getting a flu vaccine, get two doses of flu vaccine.

How many doses of flu vaccine will your kids need this year?
How many doses of flu vaccine will your kids need this year?

The first dose is a priming dose and the second, at least 28 days later, is a booster dose.

Why do we do it that way?

Because studies have shown that is the best way to do it.

We don’t need to use this same priming/booster strategy in older children and adults though.

But with recent talk that protection against the flu after a flu vaccine might wane before the end of a flu season, some folks are likely wondering if they should just get another flu shot later in the season.

“Revaccination later in the season of persons who have already been fully vaccinated is not recommended.”

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices—United States, 2018–19 Influenza Season

And the official answer is no, except for younger children getting vaccinated for the first time, you should just get one dose per season.

Why not?

Mostly because a lot of studies haven’t been done to see what effect that second dose will have. And since some studies have even suggested that regular annual flu vaccines could actually lower vaccine effectiveness, you would want to know if getting an extra flu vaccine was safe and effective before we started to do it.

Not surprisingly, someone has looked into this already. One small study, Influenza revaccination of elderly travelers: antibody response to single influenza vaccination and revaccination at 12 weeks, actually showed that a second dose in the same season “did not enhance the immune response.”

So just one flu vaccine per season.

“Prior-season vaccination history was not associated with reduced vaccine effectiveness in children, supporting current recommendations for annual influenza vaccination of children.”

McLean et al on Association of Prior Vaccination With Influenza Vaccine Effectiveness in Children Receiving Live Attenuated or Inactivated Vaccine

But do get a flu vaccine every season.

Again, while there were some reports that an annual flu vaccine could lower vaccine effectiveness, other studies have disproven this.

More on Getting a Second Flu Shot

Do More Vaccinated or Unvaccinated Kids Get Pertussis?

While this seems like a simple question, the answer is a bit more complicated than most people imagine.

Do More Vaccinated or Unvaccinated Kids Get Pertussis?

For anti-vaccine folks, the answer is clear – more vaccinated kids get pertussis. They put all of the blame for pertussis outbreaks on waning immunity. Of course, that’s not the whole story.

While 10% of kids got pertussis, unless you are at a Waldorf school, it is unusual to find that many completely unvaccinated children.
While 10% of kids got pertussis, unless you are at a Waldorf school, it is unusual to find that many completely unvaccinated children. Plus, we don’t know the vaccine history of 40% of these kids.

While it might technically be true that more vaccinated kids get pertussis in the average outbreak, that’s only because there are many more vaccinated kids!

A more accurate and useful answer, taking into account attack rates, makes it clear that a higher percentage of unvaccinated kids get pertussis in these outbreaks.

“In conclusion we have described a school-based outbreak of pertussis that may have been fueled by moderate vaccine effectiveness combined with a failure to vaccinate.”

Terrenella et al on Vaccine effectiveness of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine during a pertussis outbreak in Maine

In a pertussis outbreak in Maine, attack rates were much higher in unvaccinated kids, even though more vaccinated kids got pertussis. While 29 of 214 vaccinated kids got pertussis, a much higher percentage of unvaccinated kids got sick – 6 of 28.

That means your risk of getting pertussis was much higher if you were unvaccinated.

A 2013 pertussis outbreak in Florida is a good example that even with all the bad press it gets, the DTaP and Tdap vaccines work too. This outbreak was started by an unvaccinated child at a charter school with high rates of unvaccinated kids. About 30% of unvaccinated kids got sick, while there was only one case “in a person who reported having received any vaccination against pertussis.”

In another 2013 pertussis outbreak in Florida, this time in a preschool, although most of the kids were vaccinated, the outbreak started with “a 1-year-old vaccine-exempt preschool student.” And the classroom with the highest attack rate, was “one in which a teacher with a laboratory-confirmed case of pertussis who had not received a Tdap booster vaccination, worked throughout her illness.”

Why do so many unvaccinated kids get pertussis these days?

“We found evidence of an increase in exemption rates, spatial clustering of nonmedical exemptions, and space-time clustering of pertussis in Michigan. There was considerable overlap between the clusters of exemptions and the clusters of pertussis cases.”

Omer et al on Geographic Clustering of Nonmedical Exemptions to School Immunization Requirements and Associations With Geographic Clustering of Pertussis

Besides the fact that they are unvaccinated and unprotected?

“Children of parents who refuse pertussis immunizations are at high risk for pertussis infection relative to vaccinated children. Herd immunity does not seem to completely protect unvaccinated children from pertussis.”

Glanz et al on Parental refusal of pertussis vaccination is associated with an increased risk of pertussis infection in children.

They can’t get away with hiding in the herd.

Another important consideration – in addition to the fact that more unvaccinated kids get pertussis, when they get pertussis, it is more severe than those who are vaccinated.

“Serious pertussis symptoms and complications are less common among age-appropriate number of pertussis vaccines (AAV) pertussis patients, demonstrating that the positive impact of pertussis vaccination extends beyond decreasing risk of disease.”

McNamara et al on Reduced Severity of Pertussis in Persons With Age-Appropriate Pertussis Vaccination-United States, 2010-2012.

Still thinking of skipping or delaying your child’s pertussis vaccine?

More on Do More Vaccinated or Unvaccinated Kids Get Pertussis?

What Is a Vaccine?

You know what a vaccine is, right?

The word vaccine comes from the vaccinia virus that was in the original smallpox vaccine.
The word vaccine comes from the vaccinia virus that was in the original smallpox vaccine.

The flu shot you get each year is a vaccine.

Vaccine: A product that stimulates a person’s immune system to produce immunity to a specific disease, protecting the person from that disease. Vaccines are usually administered through needle injections, but can also be administered by mouth or sprayed into the nose.

Immunization: The Basics

The smallpox shot that Edward Jenner developed was a vaccine.

Vaccine Definitions

While that is an easy enough definition to understand, that there are many different types of vaccines does make it a little more complicated.

There are:

  • Live-attenuated vaccines – made from a weakened or attenuated form of a virus or bacteria
  • Inactivated vaccines – made from a killed form of virus or bacteria
  • Subunit, recombinant, polysaccharide, and conjugate vaccines – made from only specific pieces of a virus or bacteria
  • Toxoid vaccines – made to target a toxin that a bacteria makes and not the bacteria itself

And of course all of these types of vaccines work to produce immunity to specific diseases – vaccination.

Immunization: A process by which a person becomes protected against a disease through vaccination. This term is often used interchangeably with vaccination or inoculation.

Immunization: The Basics

What other definitions are important to know when you talk about vaccines?

  • active immunity – immunity that you get from having a disease (natural immunity) or getting a vaccine and making antibodies
  • adjuvant – a substance that helps boost your body’s immune response to a vaccine so that you can use a minimum amount of antigen, reducing side effects
  • antibodies – protective proteins that you make against antigens
  • antigens – specific substances (can be part of a virus or bacteria) that trigger an immune response
  • attenuation – a virus or bacteria that is made less potent, so that it can produce an immune response without causing disease
  • elimination – getting rid of a disease in a specific area
  • endemic – the baseline level of disease in an area
  • eradication – getting rid of a disease everywhere (smallpox)
  • epidemic – an increase in the number of cases of a disease over a large geographic area
  • herd immunity – when enough people in a community are protected and have immunity, so that disease is unlikely to spread
  • immunity – protection against a disease
  • incubation period – how long it takes to develop symptoms after you are exposed to a disease
  • outbreak – an increase in the number of cases of a disease over a small geographic area
  • pandemic – an increase in the number of cases of a disease over several countries or continents
  • passive immunity – temporary immunity that you get after being given antibodies, either via a shot of immunoglobulin or a mother’s antibodies are transferred to her baby through her placenta
  • placebo – classically defined as “a comparator in a vaccine trial that does not include the antigen under study”
  • quarantine – isolating someone so that they don’t get others sick
  • titer – an antibody count that can often be used to predict immunity

Got all of that?

So what about variolation, the process that was used before Jenner developed his smallpox vaccine? Was that also a vaccine?

It did produce immunity to smallpox, which is the basic definition of a vaccine, but still, variolation is typically concerned an immunization technique and not a vaccine.

More on Vaccine Definitions

How Are Australia’s New Vaccine Laws Working?

Have you heard about the No Jab, No Play / Pay laws in Australia?

Did Australia's new vaccine laws prompt anti-vaccine folks to put up these billboards that eventually got vandalized?
Did Australia’s new vaccine laws prompt anti-vaccine folks to put up these billboards that eventually got vandalized?

Unlike the No Pass, No Play rules that we have in Texas, in which kids can’t participate in extracurricular activities unless they pass all of their classes, No Jab, No Play / Pay has to do with getting kids vaccinated.

They were enacted in 2016 due to an increase in outbreaks of vaccine preventable disease, a rise in the spread of anti-vaccine misinformation, and more parents choosing to delay or skip their child’s vaccines. As in the United States, the real problem has been clusters of unvaccinated children in certain regions of the country, as the great majority of people in Australia vaccinate their kids.

How Are Australia’s New Vaccine Laws Working?

As expected, Australia’s new vaccine laws have been a success.

On the national level, No Jab, No Pay has meant that children need to be fully immunized “as a requirement for parents to be eligible to receive the Family Tax Benefit Part A end of year supplement, Child Care Benefit and Child Care Rebate.”

Five-year-olds in Victoria are now better protected against diseases prevented by vaccination than in any other state in Australia, new data shows.

Victoria Leads The Nation When It Comes To Vaccination Rates

But it is only in New South Wales, Queensland, and Victoria that children need to be immunized to attend childcare – No Jab, No Play. Additionally, children need to be immunized to attend kindergarten in Queensland and Victoria.

An increase in vaccination rates, by 2 to 5%, has been seen nationwide though.

What about the idea that No Jab, No Play has lead to a drop in preschool enrollments?

KATHARINA GORKA, NON-VACCINATING PARENT: I don’t think it is fair, to be honest. It makes me feel like we are a bit excluded from society, yeah.
PETER MCCUTCHEON: Did you ever think, “I’ll get my son vaccinated so I get around this pre-school problem”?
KATHARINA GORKA: No, I never thought about that.
PETER MCCUTCHEON: Why not?
KATHARINA GORKA: Because I have a set opinion on vaccinations and that is not going to change.

Some pre-schools experience drop in enrolments over ‘no jab, no play’ policy

The law about attending daycare and kindergarten just came into effect in New South Wales, in 2018, but has been in effect since 2016 in Victoria.

We will have to wait a few more months for the 2018 numbers, but preschool enrollment in Victoria was way up after they instituted their strict vaccine requirements!

In Australia during 2017, 339,243 children aged 4 or 5 were enrolled in a preschool program, representing an increase of 2.6% on the previous year’s figure. The largest growth rates were in the Australian Capital Territory (6%) and Victoria (5%).

Australian Bureau of Statistics on Preschool Education, Australia, 2017

Maybe folks just don’t want to go to care centers that had been pandering to anti-vaccine parents

Still, some vaccine advocates don’t think that No Jab, No Play / Pay laws are a good idea for Australia. Many also don’t think that it is a good idea that some Australian doctors are starting to refuse to see unvaccinated children, a practice that seems to have been exported from the United States.

Others don’t see alternatives, as they feel that they have been trying for a long time to educate parents that vaccines are safe and necessary, and this is one of the few ways that can reliably improve vaccination rates.

More on Australia’s New Vaccine Laws

Ethics and Vaccines

A lot of ethical issues come up around discussions of vaccines and vaccination.

Of course, when you talk about ethics and vaccines, you shouldn’t just think about vaccine mandates and informed consent, but also about the ethics of skipping or delaying vaccines and putting others at risk of getting a vaccine-preventable disease.

And there are also ethical issues around spreading misinformation and propaganda about vaccines (misinformed consent) to scare people away from getting vaccinated and protected.

Ethics and Vaccines

Does it surprise you that many folks don’t actually understand what the real ethical issues are in the “vaccine debate?”

Questions about ethics often come up when Dr. Bob talks about vaccines.
Questions about ethics often come up when Dr. Bob talks about vaccines.

To begin with, there is no real vaccine debate.

Vaccines are safe, effective, and necessary.

“But how can anything with known side effects be forced, knowing some will definitely be harmed?”

Dr. Bob Sears

Dr. Bob’s statement helps illustrate why this isn’t a debate.

No one is forced to get vaccinated.

And how can you say that “some will definitely be harmed” without defining what some actually means?

Severe reactions to vaccines are very rare. Fortunately, they are even more rare than the risks of a complication from a vaccine-preventable disease. And that’s why the great majority of people choose (they aren’t forced) to vaccinate and protect their kids.

Remember, a vaccine mandate that says you have to be vaccinated to attend daycare or school does not force anyone to get vaccinated. Folks still have a choice to not get vaccinated, even without access to non-medical vaccine exemptions, although they might not like what that choice entails, such as homeschooling or not being able to attend daycare or summer camp.

What about the idea of community responsibility?

Should you vaccinate your child just to protect everyone else in the community or should you just try to hide in the herd?

“One is morally free to use the vaccine regardless of its historical association with abortion. The reason is that the risk to public health, if one chooses not to vaccinate, outweighs the legitimate concern about the origins of the vaccine. This is especially important for parents, who have a moral obligation to protect the life and health of their children and those around them.”

The National Catholic Bioethics Center FAQ on the Use of Vaccines

Of course you should vaccinate them. But in getting them vaccinated and protected, you are not just protecting everyone else in the community. Getting vaccinated also protects your own child!

Similarly, when you skip or delay your child’s vaccines, it is not just your own child that is put at risk. If they get sick, especially since many vaccine-preventable diseases have long incubation periods and you can be contagious before you show symptoms, they can expose others and get them sick too. Where’s their choice?

If the people they expose are too young to be vaccinated, too young to be fully vaccinated and protected, or anyone with a problem with their immune system, the results can be tragic.

Is it ethical that someone decides to skip or delay their child’s vaccines and then, through no fault of their own, someone else dies after getting exposed to this unvaccinated child when they develop measles or chicken pox?

Remember the measles outbreaks of 2015? In addition to the large Disney Land measles outbreak, 2015 was infamous for a smaller outbreak in Clallam County.

“The death of a Clallam County woman this spring was due to an undetected measles infection that was discovered at autopsy. The woman was most likely exposed to measles at a local medical facility during a recent outbreak in Clallam County. She was there at the same time as a person who later developed a rash and was contagious for measles. The woman had several other health conditions and was on medications that contributed to a suppressed immune system. She didn’t have some of the common symptoms of measles such as a rash, so the infection wasn’t discovered until after her death. The cause of death was pneumonia due to measles. This tragic situation illustrates the importance of immunizing as many people as possible to provide a high level of community protection against measles.”

Measles led to death of Clallam Co. woman

There were five measles cases in that 2015 Clallam County, Washington outbreak, including four who were not vaccinated. The outbreak cost at least $223,223 to contain and led to the death of a woman who just happened to be at a health clinic as one of the infected people.

Want to dismiss this case as being too rare to worry about? Just look at what is happening across Europe, with the rise in measles cases and measles deaths over the last few years.

Ethically, why should you vaccinate?

That’s easy, so that your kids don’t get a life-threatening vaccine-preventable disease. And so that they don’t expose others, potentially giving them a life-threatening disease that they are too young to be vaccinated against, couldn’t be vaccinated against because they had a true medical exemption, or were vaccinated against but are still susceptible to because they now have a problem with their immune system.

Are vaccine preventable diseases not common enough for you to be concerned about these days? You know that’s because most folks vaccinate their kids, don’t you? Do we need to go back to the pre-vaccine era before more vaccine-hesitant parents will start vaccinating their kids?

“I also warn them not to share their fears with their neighbors, because if too many people avoid the MMR, we’ll likely see the diseases increase significantly.”


Dr. Bob Sears in The Vaccine Book

What about the risks of vaccines?

While vaccines are not 100% safe, they do not cause all of the vaccine injuries and vaccine-induced diseases that anti-vaccine folks push. The real risk is believing their propaganda and leaving your child unvaccinated and unprotected.

“It is UNETHICAL to expect me to sacrifice my child for yours—especially when I know that sacrifice won’t even stop the disease from spreading. It’s time for people to stop touting their “moral superiority and selflessness” when it comes to this topic; because if you really understood how this all works, there would be nothing for you to be proud of.”

Melissa Floyd (she apparently does a podcast with Dr. Bob)

Here is where the misinformed consent comes in and ethics go out the window:

And for the record, few of us think that we are morally superior to anyone else for vaccinating and protecting our kids. We just understand that many anti-vaccine folks are victims of their cognitive biases and need to do more research. And we know that it is UNETHICAL for parents to sacrifice their kids to anti-vaccine propaganda.

More on Ethics and Vaccines