Friday, July 27, 2012

Update: Washington State pertussis epidemic

Andrew received his first dose of hepatitis B vaccine minutes after he was born. My intention had been to write an entry on hepatitis B but, as you can see, I've had my hands full.

In April of this year, Washington State Health Secretary Mary Selecky declared that pertussis (whooping cough) had reached epidemic level in the state. At that time, 640 cases had been reported to the state Department of Health since the beginning of the year.

Last Friday (July 20, 2012), the Centers for Disease Control and Prevention (CDC) published a summary of the current pertussis epidemic in Washington State in the Morbidity and Mortality Weekly Report (MMWR). Between January 1st and June 16th, 2,520 cases had been reported – 13 times the number reported during the same time last year. Illinois, New York and Wisconsin have also had dramatic increases in the numbers of pertussis cases compared to last year. In fact, nearly half of all the states have reported more than double the numbers of cases in the first six months of 2012 than their total numbers of cases in 2011 (CDC, 2012a).

Overall, the national incidence of pertussis is increasing. In 2011, a total of 8,284 cases of pertussis were reported in the U.S. So far this year, 17,920 cases have been reported. One notable exception is California. A total of 7,195 cases of pertussis were reported during the 2010 epidemic in California. Last year 1,709 cases were reported in California and, so far this year, 275 cases have been reported.

I included this graph in my previous post on pertussis vaccines:

CDC, 2002
What we see is a sharp decrease in the incidence of pertussis after the introduction of whole-cell pertussis vaccine in the mid-1940's to the lowest point in 1976. Since then, there has been a gradual increase in pertussis incidence.

There are a number of factors that could be contributing to the increase in the number of pertussis cases. One is simply that pertussis is being recognized and diagnosed more frequently. Pertussis used to be thought of as a childhood disease and immunity to pertussis was believed to be life-long. We now know that immunity to pertussis wanes and that adults usually don’t have the severe symptoms that are seen in children.

The epidemiological data from the current pertussis epidemic in Washington State and the 2010 California epidemic suggests that immunity to pertussis from acellular pertussis vaccines wanes more quickly than immunity from whole-cell pertussis vaccines, which are no longer used in the U.S.

Whereas acellular pertussis vaccines contain up to 5 antigens, whole-cell pertussis vaccines contained around 3,000 antigens. Whole-cell vaccines are highly effective; unfortunately, they also have a high occurrence of adverse events ("side effects"). Acellular vaccines have fewer side effects and appear to be highly effective for the first two years after immunization, but immunity seems to wane more quickly than after immunization with a whole-cell pertussis vaccine.

So, why should my child or I receive a pertussis vaccine if I can still get pertussis anyway? There are several reasons. Even though most of the cases of pertussis are in vaccinated people, the attack ratio is much higher in unvaccinated people. Unvaccinated children are eight times more likely to get pertussis than children who have received all of the recommended doses of DTaP (CDC, 2012b). Unvaccinated children with pertussis are more likely to have severe disease, cough longer, and infect other people than vaccinated children (Baptista et al, 2006; Préziosi & Halloran, 2003; Tozzi et al., 2003).

No vaccine is 100% effective. We have known that immunity to pertussis wanes, but it now appears that immunity from acellular vaccines wanes more quickly than we thought. Nevertheless, acellular pertussis vaccines remain our best defense against pertussis.

On a personal note, one of my duties as a nurse epidemiologist in a county health department is to investigate cases of notifiable diseases. State law requires health care providers to report notifiable diseases to their local health jurisdiction (LHJ). Pertussis is one of those diseases. When the health department receives notification of a case of pertussis, one of my colleagues or I contact the parent of the child or the person with pertussis and complete a case report form. We then submit the data that we collect to the Washington State Department of Health and from there it is sent to the CDC. In this case, the CDC published their analysis of Washington State pertussis data in the MMWR cited above. In other words, the CDC report includes data that I collected.


Águas, R., Gonçalves, G., & Gomes, G. M. G. (2006). Pertussis: increasing disease as a consequence of reducing transmission. Lancet Infectious Diseases, 6(2), 112-117.

Baptista, P. N., Magalhães, V., Rodrigues, L. C., Rocha, M. A. W., & Pimentel, A. M. (2006). Pertussis vaccine effectiveness in reducing clinical disease, transmissibility, and proportion of case with positive culture after household exposure in Brazil. Pediatric Infectious Disease Journal, 25(9), 844-846.

Centers for Disease Control and Prevention. (2002). Pertussis – United States, 1997-2000. Morbidity and Mortality Weekly Report, 51(4), 73-76.

Centers for Disease Control and Prevention. (2012). Notifiable diseases and mortality table. Morbidity and Mortality Weekly Report, 61(28), ND-382-ND-395.

Center for Disease Control and Prevention. (2012). Pertussis epidemic – Washington, 2012. Morbidity and Mortality Weekly Report, 61(28), 517-522.

Offit, P. A., Quarles, J., Gerber, M. A., Hackett, C. J., Marcuse, E. K., Kollman, T. R. et al. (2002). Addressing parents’ concerns: do multiple vaccines overwhelm or weaken the infants immune system? Pediatrics, 109(1), 124-129.

Préziosi, M-P. & Halloran, E. (2003). Effects of pertussis vaccination on disease: vaccine efficacy in reducing clinical severity. Clinical Infectious Diseases, 37(6), 772-779.

Rohani, P. & Drake, J. M. (2011). The decline and resurgence of pertussis in the US. Epidemics, 3(3-4), 183-188. doi: 10.1016/j.epidem.2011.10.001.

Tozzi, A. E., Ravá, L., Ciofi degli Atti, M. L., Salmaso, S., Progetto Pertosse Working Group. (2003). Clinical presentation of pertussis in unvaccinated and vaccinated children in the first six years of life. Pediatrics, 112(5), 1069-1075.

Witt, M. A., Katz, P. H., & Witt, D. J. (2012). Unexpectedly limited durability of immunity following acellular pertussis vaccination in preadolescents in a North American outbreak. Clinical Infectious Diseases, 54(12), 1730-1735. doi: 10.1093/cid/cis287.

Friday, July 13, 2012

Ladies and gentlemen,

please allow me to introduce Andrew Craig Rollosson.

As he was walking by the Sea of Galilee, he saw two brothers, Simon who is called Peter, and his brother Andrew, casting a net into the sea; they were fishermen. He said to them, “Come after me, and I will make you fishers of men.” At once they left their nets and followed him.
- Matthew 4:18-20

The next day John was there again with two of his disciples, and as he watched Jesus walk by, he said, “Behold, the Lamb of God.” The two disciples heard what he said and followed Jesus. Jesus turned and saw them following him and said to them, “What are you looking for?” They said to him, “Rabbi” (which translated means Teacher), “where are you staying?” He said to them, “Come, and you will see.” So they went and saw where he was staying, and they stayed with him that day. It was about four in the afternoon. Andrew, the brother of Simon Peter, was one of the two who heard John and followed Jesus. He first found his own brother Simon and told him, “We have found the Messiah”
- John 1:35-41

Saturday, July 7, 2012

Immunization laws

Our son - nose, lips, chin, and cheek.
I started this blog to discuss childhood immunizations but I've spent the last six months discussing vaccines and pregnancy, adult vaccines, and some immunization principles. Our son will born soon - very soon - so it's time for me to shift gears.

A number of surveys of adults have found that the majority of parents vaccinate their children according to the recommended immunization schedule and consider their health care providers to be reliable sources of immunization information (Gust et al., 2008; Kennedy et al., 2011). Although most parents of young children in the U.S. do not remember epidemics of vaccine-preventable diseases, most parents recognize that vaccines are an important way to prevent diseases (Freed et al., 2010; Gust et al., 2005). I suspect that, other than when they register their children for school and must present their children's immunization records, most parents don't give much thought to school immunization laws. Nevertheless, given some of the comments I hear from parents as well as news stories about mandated vaccines, I think there is some confusion about vaccine laws in the U.S.

First, school immunization laws are state laws. There are no federal immunization laws.

There are two operating divisions of the U.S. Department of Health and Human Services that are involved with regulating and recommending vaccines. The Food andDrug Administration (FDA) approves and licenses vaccines marketed in the U.S. The Center for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) publishes immunization recommendations. Occasionally, there are some differences between what the FDA approves and what the ACIP recommends. For example, the FDA approved herpes zoster (shingles) vaccine for persons 50 years of age and older while the ACIP recommends shingles vaccines for persons 60 years of age and older.

Neither the FDA nor the CDC mandate vaccines. In fact, the CDC is not a regulatory agency.

In Jacobson v. Massachusetts (1905), the U.S. Supreme Court affirmed states' authority to mandate vaccines. The court recognized the duty of the state to preserve the safety of the general public. Each state has its own school immunization laws and the requirements for school entry differ from state to state. In general, the states follow the ACIP recommendations; however, some vaccines recommended by the ACIP are not required by every state. One example is human papillomavirus (HPV) vaccine. The ACIP recommends HPV vaccine for males and females ages 9 through 26 years. Currently, the only state to require HPV vaccination for school entry is Virginia (6th grade, girls only).

All states require DTaP/Tdap, MMR, polio, and varicella (chickenpox; documentation of immunity from natural infection may be acceptable) immunizations for school entry. The number of doses required varies between states as do the requirements for other vaccines such as hepatitis B, hepatitis A, meningococcal, and pneumococcal vaccines.

Just as the school immunization laws vary between states, immunization exemption laws also vary between states. There are three types of immunization exemptions: medical, religious, and personal/philosophical. Children for whom an immunization is contraindicated may obtain a medical exemption, which usually requires documentation of the reason for the exemption from a medical provider. All 50 states allow medical exemptions. Forty-eight states allow religious exemptions and 20 states allow personal/philosophical exemptions.

The requirements for obtaining an exemption vary between states. Some states require only a parent's signature on an exemption forum to obtain either a religious and/or personal/philosophical exemption. Other states have additional requirements. Last year, the Washington State legislature changed the requirement for obtaining a person/philosophical requirement. Prior to 2011, a parent or guardian could simply sign an exemption form. ESB 5005 requires the signature of a licensed health care professional who has counseled the parent on the benefits of vaccinating and the risks of not vaccinating.

Not surprisingly, states in which exemptions are easily obtained tend to have higher exemption rates (Rota et al., 2001). Several studies have concluded that nonmedical exemptions increase the incidence of vaccine-preventable diseases and increase the risk of those diseases in babies too young to have been immunized, people with medical contraindications to vaccines, and those who received the vaccine but did not develop adequate immunity (primary vaccine failure) or lost their immunity (secondary vaccine failure) (Feikin et al., 2000; Glanz et al., 2009; May & Silverman, 2003; Omer, Engler, et al., 2008; Omer, Pan, et al., 2006; Omer, Salmon, et al., 2009).

Students with immunization exemptions may be excluded from school during an outbreak of a vaccine-preventable disease (NNII, 2011). In Washington State, a local (county) health officer may require non-immunized students to be excluded from school during an outbreak (WAC 246-110-020).

Parents of infants and school-age children should review the immunization requirements for the state in which you live. See additional information below.

The ACIP recommends a dose of hepatitis B vaccine at birth, so that will be the topic of my next post.

Additional information:

Immunization Action Coalition:
National Network for Immunization Information:

Feikin, D. R., Lezotte, D. C., Hamman, R. F., Salmon, D. A., Chen, R. T., Hoffman, R. E. (2000). Individual and community risks of measles and pertussis associated with personal exemptions to immunizations. JAMA, 284(24), 3145-3150.

Glanz, J. M., McClure, D. L., Magid, D. J., Daley, M. F., France, E. K., Salmon, D. A. et al. (2009). Parental refusal of pertussis vaccination is associated with an increased risk of pertussis infections in children. Pediatrics, 123(6), 1446-1451.

Freed, G. L., Clark, S. J., Butchart, A. T., Singer, D. C., & Davis, M. M. (2010). Parental vaccine safety concerns in 2009. Pediatrics, 125(4), 654-659.

Gust, D., Brown, C., Sheedy, K., Hibbs, B., Weaver, D., & Nowak, G. (2005). Immunization attitudes and beliefs among parents: beyond a dichotomous perspective. American Journal of Health Behavior, 29(1), 81-92.

Gust, D. A., Darling, N., Kennedy, A., & Schwartz, B. (2008). Parents with doubts about vaccines: which vaccines and reasons why. Pediatrics, 122(4), 718-725.

Kennedy, A., Basket, M., & Sheedy, K. (2011). Vaccine attitudes, concerns, and information sources reported by parents of young children: results from the 2009 HealthStyles survey. Pediatrics, 127(Supple. 1). S92-S99. Retrieved June 10, 2011 from

May, T. & Silverman, R. D. (2003). ‘Clustering of exemptions’ as a collective action threat to herd immunity. Vaccine, 21, 1048-1051.

National Network for Immunization Information. (2011). Exemptions from immunization laws. Retrieved July 7, 2012 from

Omer, S. B., Enger, K. S., Moulton, L. H., Halsey, N. A., Stokley, S., & Salmon, D. A. (2008). Geographic clustering of nonmedical exemptions to school immunization requirements and associations with geographic clustering of pertussis. American Journal of Epidemiology, 168(12), 1389-1396.

Omer, S. B., Pan, W. K. Y., Halsey, N. A., Stokley, S., Moulton, L. H., Navar, A. M. et al. (2006). Nonmedical exemptions to school immunization requirements: secular trends and association of state policies with pertussis incidence. JAMA, 296(14), 1757-1763.

Omer, S. B., Salmon, D. A., Orenstein, W. A., deHart, P., Halsey, N. (2009). Vaccine refusal, mandatory immunization, and the risk of vaccine-preventable diseases. New England Journal of Medicine, 360(19), 1981-1988.

Rota, J. S., Salmon, D. A., Rodewald, L. E., Chen, R. T., Hibbs, B. F. et al. (2001). Process for obtaining nonmedical exemptions to state immunization laws. American Journal of Public Health, 91(4), 645-648.