The difference is that one (DTaP) is used as the primary series for infants and younger children (age 6 years and under) and the other (Tdap) is given to older children (age 7 years and above), teens, and adults.
Okay, that’s not the only difference.
The DTaP vaccine actually contains more diphtheria and pertussis antigens than Tdap, which is why it has the capital “D” and “P” in its name. The amount of tetanus toxoid antigens are about the same in both vaccines.
So Tdap contains the same amount of tetanus toxoid, plus a reduced amount of diphtheria and acellular pertussis antigens, as compared to DTaP.
While you would think that older children and adults would get the vaccine with the higher amount of antigens, since they are bigger, that’s not how this works. Vaccines typically start working at the injection site, so body size isn’t a key factor in determining the amount of ingredients.
As a booster dose of vaccine, the lower amount of antigens works just fine and helps reduce the risk of side effects from repeated doses that you might get with higher antigen counts.
“Existing evidence on the safety and effectiveness of MMR vaccine supports current policies of mass immunisation aimed at global measles eradication and in order to reduce morbidity and mortality associated with mumps and rubella.”
Cochrane Systematic Review on Vaccines for measles, mumps and rubella in children
Let’s see if you still are after we get all of your questions about the measles vaccine answered…
How long has the measles vaccine been around? The very first measles vaccine was licensed by John Enders in 1963. An improved measles vaccine was developed by Maurice Hilleman and licensed in 1968, and that is the measles vaccine that we still use today, at least in the United States. It was combined into the MMR vaccine in 1971.
How effective is the measles vaccine? A single dose of the measles vaccine is about 93% effective at preventing a measles infection. Two doses (the second dose was added to the routine immunization schedule in 1994) are up to 97% effective. That’s why almost all of the people who get measles in an outbreak are unvaccinated.
How long does immunity from the measles vaccine last? Immunity from the measles vaccine is thought to be life-long. It is important to understand that the second dose isn’t a booster dose, but is instead for those few folks who don’t respond to the first dose.
Who should get the measles vaccine? Everyone without a true medical contraindication should get the measles vaccine (MMR), with the first dose at 12-15 months and a second dose at 4-6 years.
Can my kids get their measles vaccine early? An advanced immunization schedule is available for kids in an outbreak or if they will be traveling out of the country. The first dose can be given as early as age 6-months, but is repeated when the child is 12 months because of concerns of interference with maternal antibodies. The official second dose can be given early too, as early as 4 weeks after the first dose, as long as the child is at least 12 months old.
Do I need a booster dose of the measles vaccine? People who are fully immunized do not need a booster dose of the MMR vaccine, but it is important to understand whether or not you are really fully immunized to see if you need a second dose. Some adults who are not high risk are considered fully vaccinated with only one dose, while others should have two doses. Are you at high risk to get measles? Do you travel, live in an area where there are measles outbreaks, go to college, or work as a health care professional?
Should I check my measles titers? In general, it is not necessary to check your titers for measles. If you haven’t had two doses of the MMR vaccine, then get a second dose. If you have had two doses of the MMR vaccine, then you are considered protected. Keep in mind that there is no recommendation to get a third dose of MMR for measles protection, although it is sometimes recommended for mumps protection during a mumps outbreak.
If my child gets a rash after getting his MMR, does that mean that he has measles? No. This is a common, very mild vaccine reaction and not a sign of measles.
Can the measles vaccine cause seizures? The MMR vaccine can cause febrile seizures. It is important to remember that without other risk factors, kids who develop febrile seizures after a vaccine are at the same small risk for developing epilepsy as other kids. And know that vaccines aren’t the only cause of febrile seizures. Vaccine-preventable diseases can cause both febrile seizures and more serious non-febrile seizures.
Why do people think that that the measles vaccine is associated with autism? It is well known that this idea originated with Andrew Wakefield, but the real question should be why do some people still think that vaccines are associated with autism after so much evidence has said that they aren’t?
What are the risks of the measles vaccine? Like other vaccines, the MMR vaccine has mild risks or side effects, including fever, rash, and soreness at the injection site. Some more moderate reactions that can rarely occur include febrile seizures, joint pain, and a temporary low platelet count. More serious reactions are even rarer, but can include deafness, long-term seizures, coma, or lowered consciousness, brain damage, and life-threatening allergic reactions.
When did they take mercury out of the measles vaccine? Measles vaccines, including the MMR, have never, ever contained mercury or thimerosal.
Why do we still have outbreaks if we have had a measles vaccine since 1963? In the United States, although the endemic spread of measles was declared eliminated in 2000, many cases are still imported from other countries. As measles cases increase around the world, that is translating to an increase in outbreaks here. Even though overall vaccination rates are good, because there are many pockets of susceptible people in areas that don’t vaccinate their kids, they get hit with outbreaks.
Can we eradicate measles? Because measles is so contagious, the vaccine does have failures, and some folks still don’t get vaccinated, there is some doubt that we can eradicate measles without a better vaccine. That doesn’t mean that the current measles vaccines can’t prevent outbreaks though…
Are you ready to get your kids their MMR vaccine so that they are vaccinated and protected against measles, mumps, and rubella?
Are you ever concerned that your kids will get their vaccines too early or too late?
For example, if your child needs a booster dose of a vaccine in a month, just how long is that?
Does it depend on which month you are in?
For intervals of 3 months or less, you should use 28 days (4 weeks) as a “month.”
Ask the Experts on Scheduling Vaccines
In general, while we often use calendar months, because it is more convenient, you can use a minimum interval of 28 days or 4 weeks as a full month, as long as we are only counting up to three months.
So a second flu shot after a dose on January 1st could be done as early as January 29th. That’s technically one month (28 days, 4 weeks) later. And no, you wouldn’t have to repeat the second dose if you got it on February 1st, as we are typically worried about the minimum intervals or spacing and not about getting the dose a little late.
For intervals of 4 months or longer, you should consider a month a “calendar month”: the interval from one calendar date to the next a month later.
Ask the Experts on Scheduling Vaccines
And just count calendar months if you are counting more than 3 months. So if you got a vaccine on January 1 and needed another 4 months later, you would return on May 1.
Why switch to using “calendar months” for longer intervals? With longer 28 day intervals, scheduling mistakes will likely be made.
So what can we say about 2018 when it comes to vaccines?
Well, we did get some new ones!
approved by the FDA in late 2017, a new hepatitis B vaccine for adults, Heplisav-B, the formal recommendation for its use from the ACIP came on February 21, 2018
although it was both approved by the FDA and formally recommended by the ACIP in late 2017, Shingrix, the new shingles vaccine, became more widely available in 2018 – well kind of – there have been a lot of shortages due to high demand for the vaccine
Vaxelis, a hexavalent vaccine that combines DTaP-IPV-Hib-HepB into one shot was FDA approved on December 21, 2018, but likely won’t be available for a few more years
And we lost one… Last year was the first full year that Menomune, an older meningococcal vaccine, was no longer available. It was discontinued because of low demand, as we began to use the newer vaccines, Menactra and Menveo instead.
a shortage of monovalent pediatric hepatitis B vaccine will continue into 2019 (doesn’t affect combination vaccines with hepatitis B)
Gardasil 9 received an expanded recommendation – women and men between the ages of 27 and 45 years can now get vaccinated and protected with this HPV vaccine
the hepatitis A vaccine got a lower age recommendation – at least in special situations – “HepA vaccine be administered to infants aged 6–11 months traveling outside the United States when protection against HAV is recommended.”
the recommendation to use a third dose of MMR to control outbreaks of mumps was formally approved
the WHO updated its recommendations for use of the dengue fever vaccine (Dengvaxia) to makes sure that only dengue-seropositive persons are vaccinated, as they found an increased risk of severe dengue in seronegative people who were vaccinated
Of the 163 million to 168 million doses of flu vaccine that will be distributed in the United States for the 2018-2019 season, more than 80% will be thimerosal free.
China had an issue with substandard DTaP vaccines made by one company in one part of the country
India had an issue with contaminated polio vaccines made by one company in one part of the country – bivalent oral polio vaccines (two strains) still contained all three strains of polio vaccine virus
If you didn’t hear about any of those things in the news, you may have heard about the death of two young children in Samoa after they received an MMR vaccine. That tragedy almost certainly was caused by an error in administering/mixing the vaccines, and not because there was anything wrong with the vaccines themselves.
Need help getting educated about vaccines? Despite continued outbreaks, 2018 was a good year for vaccine advocates and vaccine education.
That’s one of the reasons that it is important for everyone to be vaccinated, so that herd immunity levels of protection can protect those who can’t get vaccines.
Vaccines After Cancer and Chemotherapy
But what happens after they complete their cancer treatments?
“The interval until immune reconstitution varies with the intensity and type of immunosuppressive therapy, radiation therapy, underlying disease, and other factors. Therefore, often it is not possible to make a definitive recommendation for an interval after cessation of immunosuppressive therapy when inactivated vaccines can be administered effectively or when live-virus vaccines can be administered safely and effectively.”
Red Book on Immunization in Immunocompromised Children
After they complete therapy for cancer, whether it is chemotherapy or a bone marrow transplant, many children need to get extra vaccines.
In the UK, for example, 6 months after completing “standard antileukemia chemotherapy,” children get a booster dose of DTaP, IPV, Hib, MenC, and MMR.
Why just a single booster dose?
Because most kids can continue to get non-live vaccines on schedule while they are getting standard chemotherapy. They get a booster dose when they finish chemotherapy because those vaccine doses they got while receiving treatment might not be as effective as usual and typically don’t count as valid doses.
Of course, if they were missing any doses, then they might need extra doses to catch up too.
“Three months after cancer chemotherapy, patients should be vaccinated with inactivated vaccines and the live vaccines for varicella; measles, mumps, and rubella; and measles, mumps, and rubella-varicella according to the CDC annual schedule that is routinely indicated for immunocompetent persons.”
2013 IDSA Clinical Practice Guideline for Vaccination of the Immunocompromised Host
In contrast to those getting standard chemotherapy, if treatment involved a hematopoietic stem cell transplant (HSCT), then these children are essentially revaccinated:
beginning at 6 months after the HSCT, they should get 3 doses of DTaP if they are less than 7-years-old vs a dose of Tdap and 2 doses of Td if they are already 7-years-old
beginning at 3-6 months after the HSCT, they should get 3 doses of Prevnar
beginning at 6-12 months after the HSCT, they should get 3 doses of Hib
beginning at 6-12 months after the HSCT, they should get 3 doses of hepatitis B, followed by postvaccination anti-HBs titer testing
beginning at 6-12 months after the HSCT, they should get 3 doses of IPV
beginning at 6-12 months after the HSCT, they should get 2 doses of a meningocococcal vaccine (if they are already 11 to 18 years old)
beginning at 6-12 months after the HSCT, they should get 3 doses of HPV vaccine (if they are already 11 to 26 years old)
beginning at 12 months after the HSCT, one dose of the Pneumovax vaccine
beginning at 24 months after the HSCT, two doses of MMR
beginning at 24 months after the HSCT, two doses of the chicken pox vaccine
a yearly flu shot
Why not just check titers instead of repeating all of those vaccines?
“protective” concentrations or titers in this population may not be as valid as in healthy children, leaving open the question regarding what levels to use as the basis for revaccination. Furthermore, there are some vaccines for which no serological correlate of protection exists (e.g., pertussis) or for which, in routine practice, it is too difficult to have levels measured (e.g., polio).
Soonie R. Patel et al. on Revaccination of Children after Completion of Standard Chemotherapy for Acute Leukemia
In Canada, they used to check titers at 1, 3, and 5 years after the end of chemotherapy and just vaccinate when titers dropped, but they switched to giving all kids a booster dose, as it works better.
What will your child’s immunization look like after completing treatment for cancer?
Although the specific recommendations will come from your child’s treatment team, they will likely look something like the guidelines included here.
What to Know About Vaccines After Cancer and Chemotherapy
Kids often have to get revaccinated, or at least get booster doses of their vaccines, after completing treatment for cancer.
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.”
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.