Vaccine Education Center

Vaccine-Related News Archive

May 2014

Pertussis vaccine update

Pertussis, or whooping cough, is often reported in the news when an infant dies. The disease causes severe bouts of coughing, and young infants are not physiologically or immunologically prepared to fight the infection. Because of their narrow windpipes, infants have trouble breathing during the coughing spells, sometimes turning blue; and most babies need the first three doses of pertussis vaccine to be sufficiently protected from infection. For these reasons newborns and young infants are at greater risk of hospitalization and death.

While a vaccine against pertussis has been available since the early 1900s, the history of the vaccine is complex and recently-identified strains of pertussis have made the current story more interesting.

Pertussis as a cause of disease

For the purposes of this discussion, a couple of points about the biology of pertussis are important to understand:

Additional information about pertussis and the disease it causes can be found here:

Early pertussis vaccine, known as the “whole cell pertussis vaccine”

The first vaccine for pertussis was made in 1914. By the late 1940s the pertussis vaccine was combined with vaccines for diphtheria and pertussis, known as the DTP vaccine. Children received three doses of DTP, with each dose separated by about one month, and a booster dose at 1 year.

The DTP vaccine contained one protein that protected against diphtheria, one protein that protected against tetanus and about 3,000 proteins that protected against pertussis. Unfortunately, the vaccine had a high rate of side effects, most of which were attributed to the pertussis component of the vaccine. Mild side effects, such as pain and swelling as well as low-grade fever, fretfulness and drowsiness occurred in one-third to one-half of children who got this vaccine. Worse, about 1 of every 100 recipients experienced persistent, inconsolable crying, 1 of every 330 had a high fever, and about 1 of every 1,750 had seizures or experienced episodes in which they became floppy (lack of muscle control) and unresponsive. While all children recovered, these side effects were scary and led researchers to work toward a better understanding of pertussis infections and development of a second, safer pertussis vaccine.

Did you know?

During the mid to late 1940s, pregnant women were recommended to get pertussis vaccine in an effort to protect their newborn infants with maternal antibodies. 

Current pertussis vaccine, known as the “acellular pertussis vaccine”

A newer version of the pertussis vaccine became available in the 1990s. Instead of about 3,000 proteins, this acellular version contains only two to four pertussis proteins. The selected proteins are those that most commonly cause illness and allow the bacteria to infect cells in the respiratory tract. The newer version of the pertussis vaccine led to a dramatic decrease in the occurrence of side effects.

Infants and young children typically receive five doses of the vaccine known as DTaP; the first three doses, given during early infancy at 2 months, 4 months and 6 months, produce immunity. The latter two doses, typically around 15 to 18 months and again between 4 and 6 years of age, are considered booster doses — they “remind” the immune system that it has seen these disease-causing agents in the past.

Unfortunately, the medical community knew that as people got older they would become susceptible to pertussis again because the protection afforded by the vaccine given during infancy and before starting school (DTP or DTaP) was the same as the protection provided by a pertussis infection — short-term. However, the more doses of DTP or DTaP people received, the more likely they were to suffer severe (whole limb) swelling of the arm that was vaccinated. For this reason scientists designed the Tdap vaccine which contains lesser quantities of the diphtheria and pertussis vaccines; the lowercase letters in the nomenclature reflect this difference.

The Tdap vaccine is recommended for all adolescents around 11-12 years of age, and one time for adults. The exception to the recommendation for adults is that pregnant women should get the vaccine during each pregnancy, preferably during the period between 27 and 36 weeks’ gestation.

But, the pertussis vaccine story does not end there

Since the acellular pertussis vaccine became available, the U.S. has experienced increases in outbreaks of pertussis. While vaccine safety concerns have caused some to forego immunizations for their children, unvaccinated children in the community are not the main reason for these outbreaks. Researchers now understand that while the acellular pertussis vaccine has a better safety profile, it is less effective. In fact, studies have shown that children who got the DTP vaccine in infancy are less likely to get pertussis than those who got the DTaP vaccine. Further, even when older adolescents and adults get the Tdap booster vaccine, the protection decreases over time.

Additionally, a group of researchers found that some strains of pertussis that are causing disease no longer contain one of the proteins contained in the vaccines, known as pertactin. Pertactin is a protein that helps bacteria adhere to cells that line the respiratory tract. Because of this finding, some have questioned whether recent pertussis outbreaks are caused by these unusual bacteria. While researchers continue to study these strains, several pieces of information are reassuring: 

While these pertactin-negative strains should be monitored, they have not been found to be more dangerous than other strains of pertussis. Early data suggest pertactin-negative strains may be less virulent.


Pertussis vaccination is still the best choice for protecting ourselves and our children from pertussis. The vaccine is safe, but not perfect. Researchers should be urged to continue working toward a more effective pertussis vaccine. And, in the meantime, parents of young infants should make sure that visitors have had a Tdap booster and are not around the baby if they are ill. 


Atwell JE, Van Otterloo J, Zipprich J, Winter K, Harriman K, Salmon DA, Halsey NA, Omer SB. Nonmedical vaccine exemptions and pertussis in California, 2010. Pediatrics. 2013 Oct 1; 132(4):624-30.

Baxter R, Bartlett J, Rowhani-Rahbar A, Fireman B, Klein NP. Effectiveness of pertussis vaccines for adolescents and adults: case-control study. BMJ. 2013 Jul 17;347:f4249.

Klein, N. P.; Bartlett, J.; Rowhani-Rahbar, A.; Fireman, B.; Baxter, R. Waning protection after fifth dose of acellular pertussis vaccine in children. NEJM. 2012; 367: 1012-9.

Klein NP, Bartlett J, Fireman B, Rowhani-Rahbar A, Baxter R. Comparative effectiveness of acellular versus whole-cell pertussis vaccines in teenagers. Pediatrics. 2013 Jun;131(6):e1716-22.

Queenan AM, Cassiday PK, Evangelista A. Pertactin-negative variants of Bordetella pertussis in the United States. NEJM. 2013; 368: 583-4

March 2014

Measles in the U.S.

Measles was declared eliminated from the U.S. in 2000; however, over the past several years, increasing numbers of measles cases have been reported. In 2012, 55 cases of measles were reported in the U.S. In 2013, that number more than tripled to 187. So far in 2014, 71 cases of measles have been reported. Many of these cases have been linked to unvaccinated international travelers. Measles has recently been reported in New York, Connecticut, Massachusetts and California.

MMR vaccine safety

In some instances, infected individuals were unvaccinated because of concerns about vaccine safety. However, these concerns have been studied and disproven by numerous, well-controlled scientific studies.

The MMR vaccine protects against measles as well as mumps and rubella. Here’s what you should know about the MMR vaccine:


From the media

Influenza continues to occur throughout the United States

Influenza cases continue to be reported across the U.S.; however, overall the number of cases has decreased compared to previous weeks. Here’s what you should know:


High-risk groups

Anyone can get influenza and die from it even previously healthy individuals. However, some people are at higher risk of suffering complications when they are infected with influenza:

The H1N1 strain that has been circulating tends to be particularly severe in young adults, pregnant women and obese adults.


The best protection against influenza is vaccination. Although not foolproof, getting vaccinated provides your immune system a better chance to fight infection if you are exposed:


A few antiviral medications are available to treat people infected with influenza:


Influenza infographic

Learn about the importance of getting the influenza vaccine

Meningococcal disease at U.S. universities

Meningococcus serogroup B is circulating at Princeton University and University of California Santa Barbara (UCSB). Here’s what you should know:

Princeton University

As of February 20, 2014:

Learn more about the outbreak at Princeton»

University of California, Santa Barbara (UCSB)

As of March 10, 2014:

Learn more about the outbreak at UCSB»

Although serogroup B meningococcal bacteria is circulating at both universities, scientists at the CDC have found that the cases at the two universities are not linked because the students were not all infected with the same strain of the bacteria.

July 2013

Pregnancy dose of Tdap vs. “cocooning”

In June 2013, a study published in the journal Pediatrics assessed the best method for preventing infant pertussis by investigating two strategies: 1) immunizing pregnant women with a dose of Tdap vaccine between 27 and 36 weeks’ gestation or 2) immunizing parents and close contacts with Tdap vaccine after the baby is delivered, commonly referred to as “cocooning.” The results showed that immunizing pregnant women with one dose of Tdap vaccine was more successful in preventing pertussis disease and hospitalizations in infants.


Pertussis: What You Should Know (English)
Pertussis: What You Should Know (Spanish)

June 2013

Varicella vaccine effectiveness

Children 12 months of age and older were recommended to receive one dose of the varicella vaccine when it became available in 1995. In 2006, a second dose recommendation was added for children between 4 and 6 years of age. In May 2013, a study published in the journal, Pediatrics, assessed the long-term effectiveness of the varicella vaccine. Here’s what you should know:


April 2013

HPV Vaccine Safety

A recent study in the journal, Pediatrics, found that a growing number of U.S. parents are not vaccinating their daughters against human papillomavirus (HPV). Although the HPV vaccine is safe and hasn’t been linked to serious side effects, more than 16 of 100 parents cited safety concerns as the reason behind their decision. Due to misinformation about the HPV vaccine that can be found on the Internet, it can be difficult to tell what’s scientifically accurate and what’s not. Here’s what you should know about HPV vaccine safety and efficacy:

HPV vaccine safety

The HPV vaccine is safe:

HPV vaccine efficacy

Studies involving about 30,000 girls and young adults ages 9 to 26 determined that the HPV vaccine is effective in preventing:


Here are some resources to learn more about the HPV vaccine:

HPV: What You Should Know (English)»
HPV: What You Should Know (Spanish)»»

Last updated: August 2014

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.


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