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Journal Club Debunks Anti-Vaccine Myths

November 2, 2010 2 comments

READ THE REST OF THIS ENTRY AT SCIENCE BASED MEDICINE

American Family Physician, the journal of the American Academy of Family Physicians, has a feature called AFP Journal Club, where physicians analyze a journal article that either involves a hot topic affecting family physicians or busts a commonly held medical myth. In the September 15, 2010 issue they discussed “Vaccines and autism: a tale of shifting hypotheses,” by Gerber and Offit, published in Clinical Infectious Diseasesin 2009.

The article presented convincing evidence to debunk 3 myths:

  1. MMR causes autism.
  2. Thimerosal (mercury) causes autism.
  3. Simultaneous administration of multiple vaccines overwhelms and weakens the immune system, triggering autism in a susceptible host.

Gerber and Offit reviewed 13 large-scale studies that demonstrated no association between the MMR vaccine and autism. These included ecologic studies, retrospective observational studies and prospective observational studies.  The findings were consistent; the only outlier in all the studies of MMR was Dr. Andrew Wakefield’s small, discredited 1998 study, which was fully retracted by The Lancet in early 2010.

They reviewed 7 large-scale studies (again, ecologic, retrospective, and prospective) that consistently demonstrated no association between thimerosal and autism. They showed that the hypothesis was not biologically plausible, since the symptoms of mercury poisoning are distinct from those of autism and are not produced by the thimerosal in vaccines.

They showed that the overload hypothesis is not credible because

  1. The immunologic load has dropped from 3000 components in the 7 vaccines used in 1980 to less than 200 in the 14 vaccines recommended today.
  2. An infant’s immune system is capable of handling the thousands of antigens it is exposed to early in life.
  3. Vaccinated children are not more susceptible to infections.
  4. Autism is not an autoimmune disease.

READ THE REST OF THIS ENTRY AT SCIENCE BASED MEDICINE

 

 

Safety of influenza vaccine during pregnancy

October 7, 2010 Leave a comment

Today we will look at the recent recommendation by the CDC, the American College of Obstetricians and Gynecologists,  that, all people over 6 months of age, including pregnant women receive the flu vaccine. Anti-vaccination groups have already come out,  insinuating that the safety of the flu vaccine given during a woman’s pregnancy has not been established. Is that true? Are there any studies that have looked at the safety of the influenza vaccine for pregnant women? The answer is yes, at the very least there is one that I was able to find, using simply Google.

Safety of influenza vaccination during pregnancy.

Munoz FM, Greisinger AJ, Wehmanen OA, Mouzoon ME, Hoyle JC, Smith FA, Glezen WP.

Study Summary – The objective of the study was to “evaluate the safety of influenza vaccine that is administered in the second or third trimester of gestation”. A retrospective electronic database search of 5 influenza seasons (July 1, 1998, to June 30, 2003) was performed at a large multispecialty clinic in Houston, Texas. Immunization rates were calculated, and outcomes of pregnancy were compared between healthy women who received influenza vaccine, and a control group of healthy unvaccinated women who were matched by age, month of delivery, and type of medical insurance.

Results – Among 7183 eligible mother-infant pairs, only 252 pregnant women (3.5%) received the influenza vaccine. The mean gestational age at the time of influenza vaccination was 26.1 weeks (range, 14-39 weeks). No serious adverse events occurred within 42 days of vaccination, and there was no difference between the groups in the outcomes of pregnancy (including cesarean delivery and premature delivery) and infant medical conditions from birth to 6 months of age.

Conclusion – This study provides good evidence that pregnant women who receive the flu vaccine during the last 2 trimesters of the pregnancy, and their babies at least up to 6 months of age, face no more risks or complications than pregnant women who do not receive the flu shot during the last 2 trimesters of their pregnancy, and their babies up to 6 months of age. It appears the claims of the anti-vaccination crowd are rejected, at least as far as this study is concerned.  The authors concluded as such:

Influenza vaccine that was administered in the second or third trimester of gestation was safe in this study population.

3-dose 7-Valent pneumococcal vaccine use associated with increased nasopharyngeal acquisition of pneumococcal Serotype 19A Strain

October 5, 2010 Leave a comment

A recent study published in the Journal of the American Medical Association (JAMA) has found an association between the 7-valent pneumococcal vaccine (PCV-7) and an increase in nasopharyngeal (in the nose and throat) acquisition of pneumococcal serotype 19A strain, which is not one of the 7 strains the PCV-7 protects from. According to the authors of the study, a possible association had been observed between the use of PCV-7 vaccine and a rapid increase in serotype 19A strain acquisition, but studies had never been done to confirm this association, and the current study is the first one to address that concern. Let us look at it:

Pneumococcal Conjugate Vaccination and Nasopharyngeal Acquisition of Pneumococcal Serotype 19A Strains

Elske J. M. van Gils, MD; Reinier H. Veenhoven, MD, PhD; Eelko Hak, PhD; Gerwin D. Rodenburg, MD; Wendy C. M. Keijzers; Debby Bogaert, MD, PhD; Krzysztof Trzcinski, DVM, PhD; Jacob P. Bruin; Loek van Alphen, PhD; Arie van der Ende, PhD; Elisabeth A. M. Sanders, MD, PhD

JAMA. 2010;304(10):1099-1106. doi:10.1001/jama.2010.1290

Study Summary – The study was conducted in the Netherlands. 948  healthy infants, from 6 weeks up to 24 months of age, were enrolled, and followed between July 7, 2005, and February 14, 2008. Infants were randomly assigned to receive 2 doses of PCV-7 at 2 and 4 months; 2 + 1 doses of PCV-7 at 2, 4, and 11 months; or no dosage (unvaccinated control group). Nasopharyngeal swabs were obtained at the age of 6 weeks and at 6, 12, 18, and 24 months to test for the presence of the 19A strain of the pneumococcal bacteria. Rates of bacterial presence were compared between the different groups.

Results – 54 nasopharyngeal serotype 19A carriage isolates from 318 in the 2-dose group, 66 isolates from 327 in the 2 + 1-dose group, and 33 isolates from 303 in the unvaccinated were collected from 6 weeks through 24 months. The cumulative proportion who tested positive for new nasopharyngeal serotype 19A acquisition from 6 through 24 months of age was significantly higher in those having received the 2 + 1-dose PCV-7 schedule (16.2%; 95% confidence interval [CI], 12.6%-20.6%) vs those who were unvaccinated (9.2%; 95% CI, 6.5%-13.0%; relative risk [RR], 1.75; 95% CI, 1.14-2.70) but not after a 2-dose schedule (13.2%; 95% CI, 9.9%-17.4%; RR, 1.43; 95% CI, 0.91-2.25).

Conclusion – This study is methodologically sound. The sample size was fairly large, subjects were randomly assigned, and there was a proper control group. If the results of this study hold, and can be replicated, it would strongly suggest that a 3-dose of the PCV-7 pneumococcal vaccine might lead to higher rates of acquisition of the 19A strain in infants between 6 weeks and 24 months of age. It is very interesting that there were no statistically significant differences between the non-vaccinated children and the ones that had not received the 3rd dose yet. From the information that can be gleamed by the abstract of the study, the authors don’t seem to speculate on why it appears that the 3rd dose makes the difference. They conclude simply as such:

A 2 + 1-dose PCV-7 schedule was associated with an increase in serotype 19A nasopharyngeal acquisition compared with unvaccinated controls.

How should we interpret this study? By the author’s own admission, this is the first study to look at the association between PCV-7 and increased serotype 19A acquisition rates. As such, it is imperative that its results be replicated, to rule out mistakes, or other things that could have affected the results. On the other hand, the study looks to have been conducted well, and appears to have been designed properly. It provides intriguing evidence that 3 doses of the PCV-7 vaccine might be causally related to an increase in nasopharyngeal acquisition of pneumococcal serotype 19A Strain. More studies are needed to verify these results.

Until then, the best course of action is to speak to your pediatrician, and talk to her about using the 13, or the 23, valent version of the pneumococcal vaccine which also covers serotype 19A strains of the pneumococcal bacteria. You should not unilaterally decide to skip the pneumococcal vaccination completely based solely on this one study.

Categories: Pneumococcal, Safety

Vaccines don’t raise arthritis risk in adults

October 4, 2010 1 comment

READ THE FULL ARTICLE AT DOTmed.COM

Common vaccinations don’t raise risk of rheumatoid arthritis, easing fears that they’re linked to the inflammatory disease, according to a new study.

Case reports have suggested vaccines, possibly because of their immune-activating adjuvants, could trigger rheumatoid arthritis, a painful autoimmune disease caused by the body’s natural defenses attacking and inflaming joints.

But a study published online Tuesday in the Annals of the Rheumatic Diseases found no link between common vaccinations for flu, hepatitis, diphtheria and other illnesses and an increased risk for rheumatoid arthritis. The study also found no increased risk for patients getting vaccinations who had a genetic susceptibility to the disease, or who were smokers. Smoking has long been thought to be a major risk factor for the disease.

Receiving multiple vaccines also didn’t up the chances of getting afflicted by the joint disease.

“Our results indicate that immunological provocation of adults with common vaccines in their present form is not a major risk factor for RA,” write the authors, led by Camilla Bengtsson, a researcher at the Karolinska Institute in Stockholm, Sweden. “In addition, our results indicate that active immunization does not increase the risk of RA in individuals with established risk factors.”

READ THE FULL ARTICLE AT DOTmed.COM

Categories: Safety, Safety-General

Study links combination MMRV vaccine with double the risk for febrile seizures

September 13, 2010 Leave a comment

The MMRV vaccine is a combination vaccine, which combines the MMR vaccine and the Varicella vaccine in a single dose. The MMR vaccine itself is a combination vaccine, providing protection from Measles, Mumps and Rubella. A recent study, published in the journal Pediatrics, shows that the risk for febrile seizures, in the 7-10 day period following receipt of the MMRV vaccine, is twice as big as compared to receiving separate MMR & Varicella vaccines in the same day, for children 12-23 months of age.

Measles-Mumps-Rubella-Varicella Combination Vaccine and the Risk of Febrile Seizures

Nicola P. Klein, Bruce Fireman, W. Katherine Yih, Edwin Lewis, Martin Kulldorff, Paula Ray, Roger Baxter, Simon Hambidge, James Nordin, Allison Naleway, Edward A. Belongia, Tracy Lieu, James Baggs, and Eric Weintraub for the Vaccine Safety Datalink 2010;126;e1-e8; originally published online Jun 29, 2010; Pediatrics DOI: 10.1542/peds.2010-0665

Study Summary – The researchers used 2000–2008 Vaccine Safety Datalink data to compare seizures and fever visits, restricted to emergency room or hospital visits,  among children aged 12 to 23 months, during the 42 days after receipt of the MMRV vaccine, or the separate MMR + varicella vaccines. The study population included 83, 107 children vaccinated with MMRV between January 2006 and October 2008 and 376, 354 vaccinated with MMR varicella between January 2000 and October 2008.  The secondary comparison groups consisted of 145, 302 children who received MMR vaccine alone and 107, 744 who received varicella vaccine alone from 2000 to 2008. The authors monitored weekly seizure visits and compared the rates between the vaccines.

Results – After vaccination with all measles-containing vaccines, seizure incidence peaked during days 7 to 10; the most prominent peak was recorded after MMRV vaccination. During days 7 to 10, unadjusted rates for seizures were 84.6 seizures per 1000 person-years after MMRV vaccination, 42.2 seizures per 1000 person-years after MMR + varicella vaccination, and 26.4 seizures per 1000 person-years after MMR vaccination alone. Unadjusted rates during days 7 to 10 were nearly 8 times higher for MMRV and 4 and 3.5 times higher for MMR  varicella and MMR vaccination alone, as compared to Varicella vaccine alone.

Conclusion – The study looked at over 459 000 children, 12-to-23 months of age, who were vaccinated with either the MMRV vaccine, or separate MMR & Varicella vaccines, and found the MMRV to be associated with increased fever and seizures 7-10 days following vaccination. When compared to separate MMR + Varicella vaccine received at the same time, the combination MMRV vaccine was associated with a two-fold increase in risk of having a febrile seizure in the 7-10 days following vaccination. The authors estimated this meant 1 additional case of febrile seizure for every 2,300 doses of MMRV vaccine given, as compared to separate MMR & Varicella vaccines received at the same time. There was no difference in seizure risk outside of the 7-10 day window. The study shows that both MMRV, and MMR+Varicella vaccines are associated with increased seizure risk in the 7-10 day window, as compared to Varicella vaccine alone, with the risk from MMRV being twice as high as the separate MMR+Varicella vaccinations. Here is what the authors of the study had to say:

Among 12- to 23-month-olds receiving their first dose of measles-containing vaccine, the risk of fever and seizure are elevated 7 to 10 days after vaccination. The use of MMRV vaccine instead of separate MMR  varicella vaccines approximately doubles the risk for fever and febrile seizures, resulting in 1 additional febrile seizure for every 2300 doses of MMRV vaccine administered instead of separate MMR and varicella vaccines.

Bottom Line:  Talk to your pediatrician about this; it appears the best route is to take the separate MMR+Varicella vaccines as opposed to the single MMRV shot. Febrile seizures are fairly common, with 1 in 25 children experiencing at least one seizure. While witnessing a child going through one is scary, they are generally harmless. According to the National Institute of Neurological Disorders and Stroke:

Although they can be frightening to parents, the vast majority of febrile seizures are harmless. During a seizure, there is a small chance that the child may be injured by falling or may choke from food or saliva in the mouth. Using proper first aid for seizures can help avoid these hazards (see section entitled “What should be done for a child having a febrile seizure?”).

There is no evidence that febrile seizures cause brain damage. Large studies have found that children with febrile seizures have normal school achievement and perform as well on intellectual tests as their siblings who don’t have seizures. Even in the rare instances of very prolonged seizures (more than 1 hour), most children recover completely.

Between 95 and 98 percent of children who have experienced febrile seizures do not go on to develop epilepsy. However, although the absolute risk remains very small, certain children who have febrile seizures face an increased risk of developing epilepsy. These children include those who have febrile seizures that are lengthy, that affect only part of the body, or that recur within 24 hours, and children with cerebral palsy, delayed development, or other neurological abnormalities. Among children who don’t have any of these risk factors, only one in 100 develops epilepsy after a febrile seizure.

Categories: MMRV, Safety, Safety-General Tags: ,