William Schaffner, MD

Disclosures

November 02, 2011

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Vaccines at IDSA

Hello. I am Dr. William Schaffner, an infectious diseases specialist and Chair of the Department of Preventive Medicine at the Vanderbilt University School of Medicine in Nashville, Tennessee. I am at the Infectious Diseases Society of America (IDSA) Annual Meeting, here in Boston, to highlight some of the research on immunizations that is being presented.

I was really surprised when I looked at the program. There were many more abstracts on vaccines than ever before at these meetings, so what I am going to do is give you a sample of topics that were presented both orally and in the poster sessions at this meeting.

Immunize the Children, Protect the Adults

Let's talk first about herd immunity or, as it is now called, "indirect effect." When children are vaccinated, they are protected, but they also have indirect effects on protecting other people in the population such as adults. We already use 2 vaccines for which this indirect effect has been shown to be very powerful. The first is the pneumococcal conjugate vaccine, which is given to all children. The effects are impressive. In adults, particularly the oldest adults, cases of invasive, serious pneumococcal disease due to the serotypes in pneumococcal vaccine-7 dropped precipitously, as they did in the children who were immunized. How did that happen? By immunizing the children, their nasopharyngeal carriage was eliminated, so they could not give those pneumococci to adults. The adults were protected by extension -- 2 for the price of 1.

The same thing happens with the hepatitis A vaccine, which is now given routinely to children. Rates of hepatitis A have plummeted in adults because children are the great distributors of the hepatitis A virus in the population.

Rotavirus Vaccine

You probably know about rotavirus. Rotavirus is a profound, if not the most important, viral cause of diarrhea among infants and young children. Pediatricians and family physicians are now using rotavirus vaccine universally in young children. It is a winter/spring disease, but what is not usually recognized is that the same rotavirus also causes a winter/spring outbreak of diarrheal disease in adults.

Some colleagues at Northwestern University did the following study.[1] They saved all the specimens that were to go for stool culture from outpatients and inpatients over a period of time and tested them for rotavirus. They found, subsequent to the introduction of the rotavirus vaccine, the occurrence of rotavirus-related diarrhea plummeted in adults, whereas bacterial diarrheal diseases remained stable. This is a pretty clear indication that we have a herd effect -- immunize the children very comprehensively and the adults benefit too. This affirms the notion that immunizations protect not only the individual but the community as well.

Pneumococcal Vaccine

The pneumococcal conjugate vaccine, PCV-7, has now been supplanted by PCV-13, which protects against 6 more serotypes of pneumococci. PCV-7 was introduced in the year 2000; in various studies, use of the vaccine diminished infections from the serotypes in that vaccine by 70%-90% in children. During that period of time, infections from serotype 19A, one of the serotypes that was not in the vaccine, began to occur more frequently.

In February 2010, PCV-13 (the expanded vaccine) was introduced for universal practice in pediatrics. Here at the IDSA, we heard a report, "Early Trends for Invasive Pneumococcal Infections in Children Following the Introduction of the 13-Valent Pneumococcal Conjugate Vaccine."[2] This study was conducted in 8 children's hospitals around the country. The early trends revealed good news -- a 36% diminution, in those 8 hospitals, in the occurrence of invasive pneumococcal disease caused by the serotypes in PCV-13; and a 45% diminution in infection caused by 19A (the serotype that was increasing, which is included in the PCV-13 vaccine). So early trends confirmed recently presented data from the Centers for Disease Control and Prevention (CDC). A bonus is that penicillin resistance in these strains also appears to be decreasing -- 19A was a particularly resistant strain. So stay tuned, but it looks as though this is going to be another vaccine-related public health triumph.

Influenza Vaccine

Let's talk about influenza vaccine. You probably think that there isn't much to say about the influenza vaccine, but in point of fact there is. Within the last 2 years a high-dose version of the influenza vaccine has been licensed for use in adults, and just recently an intradermal version of the influenza vaccine has been licensed for the first time. This so-called "ouchless vaccine" has such a tiny needle that it only goes into, but not even through, the skin.

Here is some of the material that has been presented on influenza vaccine at the IDSA meeting. First, some bad news and good news with respect to healthcare worker immunization. This is a subject about which I have been on my soapbox for some time. You and I don't do a good enough job of immunizing ourselves, and our colleagues don't either. Only 60% of healthcare workers across the country are immunized against influenza each year. This is a patient safety issue. We don't want to give influenza to our patients.

The CDC did a survey[3] and, to my surprise, about half of the hospitals (approximately 55%) in this country now have some sort of requirement that their personnel receive the influenza vaccine. This requirement has different flavors in different places. Some places exempt students and volunteers, and others exempt individuals who don't have direct patient contact. Although a requirement is a step in the right direction, a requirement that is not enforced and has many gaps doesn't get the job done. We have to do better in protecting ourselves so we don't put our patients at risk.

Just to show you that mandates or serious requirements can have an effect, the Detroit Medical Cancer Center actually instituted a serious mandate recently and reported their experiences.[4] This medical center has 15,000 employees, and their rule was that if you weren't immunized, you had to wear a mask during influenza season. They increased their immunization rate from 62% to 92%. They acknowledge that they still have to work on that last 8%, but 92% is a lot closer to where we ought to be than 62%.

Influenza Vaccination During Pregnancy

Influenza and pregnancy is a serious business because if pregnant women get influenza, their rate of complications approaches that of senior citizens. That is why it is recommended that all pregnant women be immunized against influenza during the influenza season. Some concern has been raised about the safety of that recommendation, although there are good data to show that it is safe. However, the Kaiser Permanente System[5] compared 243 pregnant women who received influenza vaccine and a comparable number who did not and looked at the safety issue; in particular, pregnancy loss during the first 20 weeks of gestation. No difference was found, confirming the fact that influenza vaccine in pregnancy is safe. It does not cause pregnancy loss.

Vaccination in pregnancy is another "2-for." You protect the pregnant woman against the adverse effect of influenza, but you also protect the infant in the first months of life when the infant is too young to be immunized. Another study[6] showed that vaccination in pregnancy results in antibody transfer across the placenta to the babies up to 4 months and even longer. Vaccinated and unvaccinated mothers were compared, as were their infants. This is another great reason to vaccinate during pregnancy -- you protect the pregnant woman and you will also protect that newborn during the first months after birth.

In another study,[7] researchers from the Jefferson Medical Center looked at a group of postpartum women who were asked, "What are your concerns about being immunized during pregnancy?" They discovered that fewer of these women were concerned and more were accepting of immunization during pregnancy.

Other Studies, New Vaccines on the Horizon

Influenza vaccine contains protection against 3 antigens. They are now studying influenza vaccines with 4 antigens: 2 A antigens and 2 B antigens. Two studies were done,[8,9] one with the injectable vaccine, another with the nasal spray variety, and both methods worked comparably with no safety issues.

I would like to turn to new vaccines and tell you what is on the horizon. Clostridium difficile is a candidate vaccine that was tested for its immunogenicity against toxin A and B and was found to be very immunogenic.[10] It seems to be well-tolerated in patients, so we may have a C difficile vaccine in our future.

Lastly, a new investigative hepatitis B vaccine that has an adjuvant-like product in it has been developed.[11] It was tested specifically in patients with type 2 diabetes. It was given in 3 doses and compared with the standard hepatitis B vaccine that is given in 3 doses. This experimental vaccine was found to be more immunogenic, even after 2 doses. So once again, in looking to the future, there may be another hepatitis B vaccine available.

Thanks for your attention. Keep vaccinating! This is Bill Schaffner for Medscape.

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