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History of Vaccines Blog

February 21, 2017  Karie Youngdahl

Are you a glass half empty or glass half full type of person? Your orientation along the optimism-pessimism spectrum will determine whether you think this year’s seasonal influenza vaccine is a moderate success or near failure. The Centers for Disease Control and Prevention released its interim estimate of the 2016-17 influenza vaccine effectiveness (VE) last week: the vaccine appears to be 48% effective at preventing physician-attended influenza illness.This VE estimate is similar to last year’s estimate of 47% VE. You can see a table of VE for 2004-16 here. How does the CDC get these data? CDC used five study sites, where they enrolled patients aged ≥6 months seeking outpatient medical care for an acute respiratory illness (ARI) with cough, within 7 days of illness onset. Researchers interviewed study subjects or their parents to collect respiratory specimens, demographic data, health status, symptoms, and 2016–17 influenza vaccination status. Specimens were tested at U.S. Flu Vaccine Effectiveness Network laboratories using CDC’s real-time reverse transcription – polymerase chain reaction (rRT-PCR) protocol for detection and identification of influenza viruses.

Posted in: Influenza, Public Health

January 11, 2017  Karie Youngdahl

Robert F. Kennedy Jr.'s announcement yesterday that president-elect Donald J. Trump asked him to chair a government commission on "vaccine safety and scientific integrity" has prompted a deluge of responses on social media, on blogs, and in the media in general. Though he calls himself (and Trump) "very pro-vaccine," Kennedy has been a dogged pursuer of the discredited connection between vaccination and autism and other neurodevelopmental disorders. If Kennedy's statement about his appointment is true -- and a Trump spokesperson has not quite confirmed it -- public health and medical workers are right to be concerned about the effect this commission may have on public perception of vaccines. 

Posted in: General, Public Health

November 10, 2016  Karie Youngdahl

What does the United States president-elect have to say about vaccines?

Donald J. Trump has frequently stated that he believes that vaccines can cause autism, as in the Tweets shown here. In one of the primary debates, he dialed back his criticism a bit, stating, “I am totally in favor of vaccines, but I want smaller doses over a longer period of time.” But as Tara Haelle, a blogger at wrote, “Vaccines are very precisely manufactured to include only what is absolutely necessary to induce enough of an immune response that the body can protect itself against those diseases. So a smaller dose wouldn’t protect a child. It would stick a child with a needle for no reason at all. And spreading out vaccines? That just increases the risks to the children, including leaving them more susceptible to the diseases for a longer period of time. Trump is not ‘totally in favor of vaccines’ if he doesn’t want children protected from the diseases above as early as possible.” In contrast, in 2015, Hillary Clinton Tweeted, “The Science is clear: The earth is round, the sky is blue, and #vaccineswork. Let’s protect all our kids. #GrandmothersKnowBest.”

Posted in: General, Public Health

September 30, 2016  Karie Youngdahl

The World Health Organization Region of the Americas has achieved a milestone in disease elimination – the Pan American Health Organization (PAHO) on September 27, 2016, declared the Americas to be free of endemic measles. In the pre-vaccine era, the WHO estimates that measles killed 2.6 million children per year globally, and so measles elimination has done a great deal to combat a major threat to child health. The Region of the Americas is the first of the six WHO regions to eliminate transmission of measles. The United States was certified measles-free in 2000, and the last cases of endemic measles were reported in other countries of the region in 2002. The International Expert Committee for Documenting and Verifying Measles, Rubella, and Congenital Rubella Syndrome Elimination in the Americas was responsible for collecting reports from region countries to certify that measles has in fact been eliminated. Polio (certification in 1994), rubella (2015) and smallpox (1971) have been eliminated from the region as well, and, of course, smallpox has been eradicated globally (certification in 1980).

Posted in: Measles, Public Health

September 27, 2016  Karie Youngdahl

Carley Roche, an intern here at The College of Physicians of Philadelphia, wrote today's blog post. In December 1924 the city of Philadelphia experienced an uptick in the incidence of smallpox with 9 new cases of the disease. While there had been a few reported cases earlier in the year, it soon became apparent in early January 1925 that the December outbreak might be more severe than the others, as the first smallpox death occurred in Philadelphia in more than 12 years. The Department of Public Health would spend the next 6 months quarantining and vaccinating citizens of the city in order to prevent a massive outbreak of smallpox beyond the city limits.

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May 17, 2016  Karie Youngdahl

We know so little about Zika virus that we can’t even spell it correctly. Scott C. Weaver, MS, PhD, visiting Philadelphia from the University of Texas Medical Branch at Galveston, noted that the forest where Zika virus was discovered in the 1940s is actually spelled Ziika. Weaver brought years of research experience to his talk Monday, May 16, at The College of Physicians of Philadelphia. He is an arbovirus specialist and has worked extensively on Chikungunya virus, and, even before the current Western Hemisphere Zika virus epidemic, on Zika virus itself. Given that human cases of Zika virus disease were not known until the 1950s and that 80% of Zika cases present with no symptoms, it’s not surprising that we don’t know more about the virus and how it works. Before 2007, only 14 human cases had been diagnosed. Weaver traced the spread of Zika virus across the globe, showing a CDC map representing incidence of Zika virus antibodies and infection in local populations throughout many African and Asian countries. The virus almost certainly originated in Africa at least a millennium ago; about 50-100 years ago it spread to Asia. In 2007 the virus jumped to Yap Island from Asia, with a population of about 7,000 people, most of whom became infected. Then, in 2013, it moved to French Polynesia, with more than 100,000 people to potentially infect. French Polynesians then started to transport the virus around the world, probably to Brazil in late 2013. With this move to South America, hundreds of millions of people are now susceptible to infection. 

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May 12, 2016  Karie Youngdahl

The College of Physicians of Philadelphia is pleased to announce a public program on Monday, May 16, 2016, at 8 am (breakfast at 7:30am) on the Zika virus epidemic. Scott C. Weaver, PhD, of the Institute for Human Infections and Immunity at the Galveston (Texas) National Laboratory, and Professor, Departments of Pathology and Microbiology & Immunology at the University of Texas Medical Branch at Galveston, will speak about current efforts toward understanding Zika virus pathophysiology and epidemiology and building an effective Zika virus vaccine. Paul A. Offit, MD, vaccine developer and chief of infectious diseases of the Children’s Hospital of Philadelphia, will comment.

Posted in: General

April 20, 2016  Karie Youngdahl

At Tuesday’s sessions of the National Foundation for Infectious Diseases Annual Conference on Vaccine Research, vaccine scientists were moderately hopeful about developing an effective Zika virus vaccine. Their hope stems both from precedent and from the relatively simplicity of Zika virus: several effective vaccines for related flaviviruses have been developed, and there appears to be only one serotype of Zika virus, unlike, for example, dengue virus, which has four types. Colonel Paul B. Keiser, MD, Walter Reed Army Institute of Research, described the other flavivirus vaccines and the lessons they offer for Zika. Yellow fever vaccine has been used since the 1930s and is exceptionally effective, although it does present serious risks to certain individuals. An inactivated vaccine for tick borne encephalitis has been available in Europe since the 1970s. This vaccine doesn’t have the effectiveness profile of yellow fever vaccine and must be given in a three-dose series with boosters every 3-5 years. The Japanese encephalitis vaccine is another model for Zika vaccine: it is formalin inactivated and given generally in a three-dose series

Posted in: General, Public Health, Yellow Fever

April 18, 2016  Karie Youngdahl

At the National Foundation for Infectious Diseases Annual Conference on Vaccine Research, presenters drew pointed comparisons between the 2014-15 Ebola epidemic and the current Zika virus disease epidemic. A session on multi-sector global efforts to test an Ebola virus disease vaccine (EVD) brought together representatives from the US Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO), and the Norwegian Institute of Public Health. Anne Schuchat, MD, Principal Deputy Director of the CDC, prefaced her talk by noting that the West African EVD epidemic was the largest outbreak CDC has been involved in and involved ten times as many cases as all previously known EVD outbreaks combined. So, she says, we learned a great deal about the disease that we hadn’t known before, such as the persistence of Ebola virus in body fluids long after initial infection.

Posted in: General, Public Health

March 16, 2016  Karie Youngdahl

Today's blog post is by Carley Roche, a recent graduate from Drexel University and an intern here at The College of Physicians of Philadelphia. War is difficult on everyone, from the soldiers risking their lives to the civilians who get caught up in these violent affairs. While larger armies and more advanced weapons can aid in victory, an often overlooked variable in war chooses no allegiance: disease. One of the most devastating diseases throughout history during wartime has been typhus. Typhus is a bacterial disease caused by Rickettsia bacteria. There are two types of the disease--endemic typhus and epidemic typhus. Rickettsia typhi causes endemic typhus, also known as murine typhus, and is the least virulent. Spread to humans by fleas on animals such as cats, opossums, raccoons, and rats, most notably from the Norway rat, victims of endemic typhus will experience a bodily rash, high fever, nausea, vomiting, discomfort, and diarrhea. Rickettsia prowazekii causes epidemic typhus, which is spread via lice. Symptoms are similar to endemic typhus; they are, however, much more severe and can include delirium, hypotension, and even death.

Posted in: General