Tag: waning immunity

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?

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?

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.

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. 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?

Why Do You Need to Get a Flu Vaccine Each Year?

A yearly flu vaccine is the best way to protect yourself and your family against the flu.

But why do you need to get a flu vaccine each and every year?

Why Do You Need to Get a Flu Vaccine Each Year?

Hopefully we will one day have a universal flu vaccine that covers all flu strains and offers longer lasting protection.

Most folks know we don’t have that flu vaccine yet…

“A flu vaccine is needed every season for two reasons. First, the body’s immune response from vaccination declines over time, so an annual vaccine is needed for optimal protection. Second, because flu viruses are constantly changing, the formulation of the flu vaccine is reviewed each year and updated as needed to keep up with changing flu viruses. For the best protection, everyone 6 months and older should get vaccinated annually.”

CDC on Key Facts About Seasonal Flu Vaccine

So because the protection from the flu vaccine wanes or wears off relatively quickly, even if the flu vaccine strains don’t change from one year to the next, you should get a new flu vaccine.

How long does the protection from the flu vaccine last?

“An analysis from the 2011–12 through 2013–14 seasons noted protection ranging from 54% to 67% during days 0 through 180 postvaccination.”

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

The flu vaccines takes about two weeks to become effective and should then last for at least six months – long enough to get you through the average flu season.

“A number of observational studies and a post hoc analysis from a randomized controlled trial have reported decreases in vaccine effectiveness (VE) within a single influenza season, with increasing time postvaccination. Waning effects have not been observed consistently across age groups, virus subtypes, and seasons; and observed declines in protection could be at least in part attributable to bias, unmeasured confounding, or the late season emergence of antigenic drift variants that are less well-matched to the vaccine strain. Some studies suggest this occurs to a greater degree with A(H3N2) viruses than with A(H1N1) or B viruses . This effect might also vary with recipient age; in some studies waning was more pronounced among older adults and younger children. Rates of decline in VE have also varied.”

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

That means it should last past the peak of the average flu season, which is typically between December and March.

And in most young, healthy people, the protection likely lasts even longer.

Make sure you are vaccinated well before flu season starts. — Make sure you are vaccinated well before flu season peaks, which since 1982 has occurred as early as October and as late as March, but is most common in February.

Still, there is some concern that the protection from the flu vaccine can wear off during a flu season, especially if you are very young, very old, or have chronic medical problems, and you get your flu vaccine early and you get exposed late – in April or May.

Of course, that’s not a good reason to delay getting a flu vaccine though, as waiting too long might leave you unprotected if flu peaks early, in October or November.

What to Know About Why You Need the Flu Vaccine Every Year

Since the flu vaccine strains can change and protection doesn’t last from season to season, get a flu vaccine each year. It’s the best way to protect yourself and your family against the flu.

Can Vaccinated Children Be Asymptomatic Carriers of Pertussis?

Why do anti-vaccine folks like to talk about baboons so much?

“Did you know that a study showed that baboons injected with whooping cough vaccine became infected with whooping cough anyway – and silently spread the disease to other baboons for 35 days?”

Anti-vaccine Meme

Is it because baboons are used in the study of vaccines?

That’s part of it, at least when they can find a study where they can cherry pick the results to suit their needs.

The Baboon Study

Like most anti-vaccine talking points, this one about baboons, has some truth to it.

An adult male baboon. Photo by Elizabeth Miller

There was a baboon study with the pertussis vaccine and it found that previously vaccinated baboons could develop asymptomatic carriage of the pertussis bacteria after they were intentionally infected.

Here is where it is important to note that an infection is different than a disease.

The example that many people are familiar with is tuberculosis. It is common to have a TB infection without any signs or symptoms and to not feel sick. The only reason we know that they have TB is because they had a positive TB test.

Unfortunately, about 5 to 10% of these people with TB infections can eventually develop TB disease, with coughing, weight loss, night sweats, fever, and chest pain, etc.

It is kind of the same with the baboons in the study. Twenty-four hours after two previously vaccinated baboons were inoculated with pertussis bacteria in the back of their nose and trachea, an unvaccinated baboon was put in each of their cages.

The vaccinated baboons continued to have pertussis bacteria in their noses, which the researchers had put there, for up to 35 days. And they were able to eventually pass the pertussis bacteria to the unvaccinated baboons in their cages. Vaccinated baboons also became infected or colonized after they were put in a cage with an intentionally infected unvaccinated baboon.

“…animals did not cough and showed no reduction of activity, loss of appetite, or other outward signs of disease.”

Warfel et al on Acellular pertussis vaccines protect against disease but fail to prevent infection and transmission in a nonhuman primate model

The vaccinated baboons were infected, but they never did develop symptoms of pertussis.

What Does The Baboon Study Mean?

One thing that is for sure – the baboon study found that the pertussis vaccines work. Only unvaccinated baboons got sick with pertussis.

But does this study explain our current outbreaks of pertussis?

Are vaccinated people becoming colonized and then getting others sick?

I guess it is possible, but we are not baboons in a cage with other baboons. How would we spread a respiratory disease, even if we did become colonized with the bacteria, if we don’t have symptoms?

It may explain part of our outbreaks though.

If vaccinated people do commonly become colonized with pertussis bacteria, then they might very well test positive for pertussis even though they don’t have symptomatic pertussis disease. So when they develop a cold or bronchitis and are found to have a positive pertussis test, then couldn’t that test just indicate that they have a pertussis infection and not disease, even though something else is actually causing their symptoms?

That’s what we think happens with strep carriers, right?

That’s kind of what the baboon study found. All of the baboons tested positive, but only the unvaccinated baboons had symptomatic pertussis disease.

“Baboons vaccinated with wP vaccines exhibit a level of protection that is intermediate between convalescent animals and aP-vaccinated animals. They exhibit no outwards signs of disease and are initially colonized to the same high level as aP-vaccinated animals but clear the infection more rapidly.”

Pinto et al on Pertussis disease and transmission and host responses: insights from the baboon model of pertussis.

It is interesting to note that the baboon study also found that baboons who had received whole cell pertussis vaccines also became carriers. They just didn’t stay carriers for as long as the baboons who got the newer acellular pertussis vaccine. But since they were still carriers, if asymptomatic transmission is such a big problem, wouldn’t it have been a big problem back in the day when everyone got whole cell pertussis vaccines?

The Debate Over Asymptomatic Carriage

Most vaccines prevent the spread of disease.

Do the pertussis vaccines?

Most folks still think so.

“The baboon model pioneered by Warfel et al. is without question a game-changer, shedding light on the impact of vaccination on disease and infection. However, the view it affords is clearer with respect to immunity and pathology than with respect to transmission. We point out that the extrapolation of the possibility of transmission from vaccinated baboons in the laboratory to the probability of transmission from vaccinated humans in the population is unwarranted. More work is needed to elucidate the relative transmissibility of infections in vaccinated vs. unvaccinated hosts. The evidence adduced above suggests, however, that vaccination with aP must have a strong effect on transmission as well as disease.”

Matthieu Domenech de Cellès et al on Epidemiological evidence for herd immunity induced by acellular pertussis vaccines

Even the author of the baboon study has said that “We agree that these data should not be directly extrapolated to pertussis transmission in humans. Although baboons are >96% genetically similar to humans, there are likely differences in how the species respond to vaccination and infection. We also agree that aP-vaccinated infected people are likely less efficient at transmitting pertussis compared with unvaccinated infected people, although it is not clear to what extent.”

Others think that asymptomatic carriage of pertussis might behind a lot of our recent outbreaks. Or at least what helps them grow so large.

Still, it is important to remember that unvaccinated folks do play a role in these outbreaks too. In a pertussis outbreak at a Florida preschool, in which most kids were vaccinated, the outbreak was started by a vaccine-exempt toddler.

And we have seen this in many other areas and it has been confirmed by many studies. Whatever else is contributing to pertussis outbreaks, like waning immunity, they are also associated with vaccine refusal.

“Counties with higher exemption rates had higher rates of reported pertussis among exempted and vaccinated children when compared with the low-exemption counties.”

Imdad et al. on Religious exemptions for immunization and risk of pertussis in New York State, 2000-2011.

But what if the DTaP and Tdap vaccines do cause folks to be asymptomatic carriers?

Even if that is true, understand that these vaccines don’t actually infect you, making you a carrier. They just might not prevent you from becoming a carrier if you are exposed to someone else with pertussis. While that might be a good reason to develop a new and better pertussis vaccine, it certainly isn’t a reason to skip or delay your child’s vaccines now.

Remember that even with our current outbreaks, rates of pertussis were much higher in the pre-vaccine era.

What to Know About Vaccines and Asymptomatic Carriers of Pertussis

The role of asymptomatic carriers and pertussis is controversial, but it certainly isn’t a reason to skip or delay your child’s vaccines.

Which Vaccines Don’t Prevent the Spread of a Disease?

As most folks know, Dr. Bob Sears has been put on probation by the California Medical Board.

Most vaccines don't prevent the spread of diseases? — Most vaccines don’t prevent the spread of disease???

Surprisingly, that hasn’t kept him from posting dangerous misinformation about vaccines, including his latest idea that “most vaccines don’t prevent the spread of a disease.”

Which Vaccines Don’t Prevent the Spread of a Disease?

If vaccines don’t prevent the spread of disease, then how did we eradicate, eliminate, and control so many diseases?

Dr. Bob Sears actually reassured parents that measles wasn't deadly in developed countries, neglecting to mention the dozens of people who have died in outbreaks in Europe - another well-nourished population with lower vaccination rates than the U.S. — At least seven people have died in Italy with measles over the last few years. That’s not so good for Italy.

When was the last time you saw someone with small pox, rubella, diphtheria, or polio, for example?

It is true that vaccines don’t prevent the spread of some infections though.

There is tetanus, for example, but guess what?

Tetanus isn’t contagious.

Any others?

Well, unlike most other vaccines, the meningococcal B vaccines are not thought to decrease nasal carriage of the meningococcal B bacteria. So if you are vaccinated and an asymptomatic carrier of the bacteria, you could theoretically spread it to someone else, as could someone who is unvaccinated.

Still, the MenB vaccines can protect you from getting actual meningococcal B disease, and if you don’t have meningococcemia or meningococcal meningitis, you won’t expose and spread it to someone else. That’s why the MenB vaccines are especially useful in outbreak situations.

Any others? After all, Dr. Bob did say that “most vaccines don’t prevent the spread of a disease.”

Vaccines That Don’t Prevent the Spread of a Disease

There are a few other examples of vaccines that don’t prevent the spread of a disease.

“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

Of course, any vaccine that is delayed or skipped won’t work to prevent the spread of a disease.

Just like they are seeing measles outbreaks and deaths now, because of low vaccination rates, in Ukraine there were 17,387 cases of diphtheria and 646 deaths from 1992 to 1997. Also high, were cases of measles (over 23,000 cases in 1993) and pertussis (almost 7,000 cases in 1993).

And because of waning immunity, vaccines don’t do as good a job of preventing the spread of pertussis and mumps as we would like. Still, that’s only when the vaccines don’t work, and even then, as Dr. Bob says, they do work to reduce the severity of symptoms. During recent mumps outbreaks, the rates of complications are far below historical levels. The same is true for pertussis.

Have you ever seen or heard an unvaccinated child with pertussis? It is truly heartbreaking, especially when you realize how easily it could be prevented.

We typically see the same thing with flu. Even when the flu vaccine isn’t a good match or isn’t as effective as we would like, it still has a lot of benefits, including reducing your risk of dying.

“IPV induces very low levels of immunity in the intestine. As a result, when a person immunized with IPV is infected with wild poliovirus, the virus can still multiply inside the intestines and be shed in the faeces, risking continued circulation.”

Inactivated poliovirus vaccine

Does the fact that IPV, the inactivated polio vaccine, can sometimes lead to infections and shedding mean that it doesn’t prevent infections?

Of course not!

“IPV triggers an excellent protective immune response in most people.”

Inactivated poliovirus vaccine

Most people vaccinated with IPV will be immune, won’t get wild polio, and so won’t be able to get anyone else sick.

“Vaccines reduce disease by direct protection of vaccinees and by indirect protection of nonimmune persons. Indirect protection depends on a reduction in infection transmission, and hence on protection (immunity) against infection, not just against disease. If a vaccine were to protect only against disease, and not at all against infection, then it would have no influence on infection transmission in the community and there would be no indirect protection (vaccination of one person would have no influence on any others in the community). It would be possible to reduce disease with such a vaccine but not to eradicate the infection.”

Plotkin’s Vaccines

But because IPV doesn’t provide indirect protection, we still use OPV in parts of the world where polio is more of a problem.

Vaccines work. Even the few that don’t prevent the spread of infections, still help to reduce disease.

What’s the Difference Between Infections and Disease?

Wait, is there a difference between infection and disease?

Yes there is, something that Dr. Bob, who actually wrote a book about vaccines, seems to have overlooked.

An infection is simply the presence of a virus, bacteria, or other organism in your body.

A disease, on the other hand, is a virus or bacteria in your body causing signs and symptoms.

All vaccines work to prevent disease, or at least they do when you actually get vaccinated.

A very few don’t prevent infections and the spread of infections, but that is not a good reason to skip or delay your child’s vaccines. In fact, it is one of the reasons why it is important to have high vaccination rates! Even natural infections don’t always keep you from becoming asymptomatic carriers that can infected others. Many people who have natural typhoid (remember Typhoid Mary?) and hepatitis B infections go on to become chronic carriers without any symptoms, but still able to infect others.

If you understand that a few vaccines don’t prevent the spread of infections, then you should understand that you can’t hide in the herd and expect to be protected, even though most folks around you are vaccinated.

What to Know About Vaccines and the Spread of Disease

Despite what Dr. Bob says, almost all vaccines work to prevent the spread of disease and infections, at least they do when you get your kids vaccinated.

Is Mutating Mumps More Than the MMR Can Manage?

It is not news that we have been seeing more cases of mumps in recent years.

It is also isn’t news that many of these folks are vaccinated.

“Long Beach has been hit with a mumps outbreak that is vaccine-resistant. According to health officials in the Long Island town, almost two dozen individuals are believed to have contracted the virus, with four confirmed cases and at least 14 suspected ones.”

Natural News

That sites like Natural News is putting out misinformation about vaccine-resistant strains of mumps also shouldn’t be news to anyone.

Why Do Folks Think That Vaccine-Resistant Viruses Are Causing Mumps Outbreaks?

So are vaccine-resistant mumps viruses causing outbreaks?

There is no good evidence of that and plenty of evidence that our current vaccines, even though they aren’t perfect, do cover all wild strains of mumps.

Unfortunately, it might not be surprising that some folks are confused about vaccine-resistant mumps viruses, when we have health officials saying things like:

“Sometimes nature throws a strain at us that might have mutated a little bit, and coverage of the vaccine is not 100 percent.”

Dr. Lawrence Eisenstein, Nassau County Health Commissioner

Dr. Eisenstein’s “might have mutated a little bit” comment got twisted into “the outbreak is most likely attributable to a new strain of the virus that is resistant to vaccines” by health reporters

And out of Arkansas, where there have also been large mumps outbreaks:

“We are actually to the point that we are worried that this vaccine may indeed not be protecting against the strain of mumps that is circulating as well as it could.”

Dr. Dirk Haselow, Arkansas State Epidemiologist

Of course, to say that the vaccine may not be protecting folks “as well as it could” doesn’t mean it doesn’t work because the wild type mumps virus has evolved or mutated enough to surmount our current MMR vaccine.

Is Mutating Mumps More Than the MMR Can Manage?

Although anything is possible, we fortunately have plenty of research that says that the mumps virus hasn’t mutated and that the MMR still works.

During an outbreak, universities make sure students are up-to-date with their MMR vaccines. — During an outbreak of mumps, some kids are getting a third dose of the MMR vaccine.

In fact, although the MMR vaccine is made from the A strain or genotype of mumps, it provides good protection against all 12 known strains of wild mumps viruses, including genotype G that has been causing most of the recent outbreaks.

But how can it cover a different strain of virus that isn’t in the vaccine?

Because not all viruses and vaccines are like influenza.

“The genotyping of the mumps virus is based on the Small Hydrophobic (SH) protein, a nonstructural protein and genetically the most variable one. Based on the SH-protein 12 different mumps viruses were detected up to now. In recent epidemics in Western countries the genotype G was mainly detected, while the mumps viruses used in the live attenuated mumps vaccines belong to genotype A (Jeryl Lynn) and to a lesser extent to genotype B (Urabe). However, antibodies against the SH protein have not yet been observed in human serum. It is, therefore, unlikely that antibodies against the SH protein play an important role in antibody-mediated virus neutralization.”

Sabbe et al. on The resurgence of mumps and pertussis

It is well known that you need a very specific match of the flu vaccine to the wild flu virus that is going around to get good protection, but for many other viruses, the differences that determine the strain or genotype have nothing to do with how antibodies will recognize the virus.

“Since mumps virus is monotypic, vaccine from any strain should provide lifelong protection against subsequent infection.”

Palacios et al. on Molecular Identification of Mumps Virus Genotypes from Clinical Samples: Standardized Method of Analysis

Like measles, mumps is a monotypic virus.

“Studies have demonstrated that blood sera from vaccinated persons cross-neutralizes currently circulating mumps strains.”

CDC on Mumps for Healthcare Providers

And like measles, the mumps vaccine (MMR), protects against all strains of wild mumps viruses.

“Compared with attack rates of 31.8%–42.9% among unvaccinated individuals, attack rates among recipients of 1 dose and 2 doses of the Jeryl Lynn vaccine strain were 4%–13.6% and 2.2%–3.6%, respectively.”

Dayan et al. on Mumps Outbreaks in Vaccinated Populations: Are Available Mumps Vaccines Effective Enough to Prevent Outbreaks?

And like other vaccines, the mumps vaccine (MMR) works.

Waning immunity may be an issue, but that certainly isn’t a reason to skip or delay this vaccine and put your kids, and everyone else, at risk to get mumps.

What to Know About Mumps Strains and Outbreaks

The MMR vaccines covers all strains of mumps and getting fully vaccinated is the best way to make sure your kids don’t get mumps.

Why Do Some Vaccines Need Boosters?

Vaccines work.

They aren’t perfect though, which is why some vaccines need booster doses to help them provide long lasting protection.

Why Do Some Vaccines Need Boosters?

To be clear, just because you get more than one dose of a vaccine, that doesn’t make it a booster dose.

For example, infants get multiple doses of the DTaP, polio, Hib, hepatitis B, Prevnar, and rotavirus vaccines, but those are part of the primary series for those vaccines. They aren’t boosters.

“A “classical” prime-boost immunization schedule is, thus, to allow 4 to 6 months to elapse between priming and booster doses, hence the generic “0-1-6 month” (prime-prime-boost) schedule. Secondary antigen exposure thus results in the production of higher-affinity antibodies than primary responses.”

Plotkin’s Vaccines (Seventh Edition)

Getting the booster shot in a vaccine series is important to get full protection. — Getting the booster dose in a vaccine series is important to get full protection.

Classic booster doses are the:

4th and 5th dose of DTaP
2nd dose of hepatitis A
3rd dose of hepatitis B
4th dose of Hib
3rd dose of HPV
4th dose of Prevnar
4th dose of polio
2nd dose of meningococcal vaccines
most Tdap doses (if you are not due for a Tdap booster and are getting a dose because you are pregnant, than that probably wouldn’t be considered a booster dose)
2nd dose of Varivax (chicken pox vaccine)

But why do we need these booster doses?

While one or more doses of the primary series of the vaccine leads to the production of plasma cells and protective antibodies, the booster dose then causes a secondary immune response and the production of more long-lived plasma cells. That’s how we get higher levels of protective antibodies that will last longer.

Which Vaccines Don’t Need Boosters?

In general, live vaccines don’t need booster doses.

So why do we get a second dose of MMR?

This isn’t a classic booster dose. It protects the small percentage of people who don’t respond to the first dose.

Some folks may need a booster dose of the MMR vaccine in certain circumstances though, specifically if they are caught up in a mumps outbreak.

What to Know About Vaccine Booster Doses

Some vaccines need booster doses to help you get full protection. Don’t skip them.

VAXOPEDIA

Can I Get a Second Flu Shot for Extra Protection?