Chickenpox, which is caused by the varicella-zoster virus, has continued declining in the United States since 2006, when doctors began routinely recommending a second dose of chickenpox (varicella) vaccine, U.S. health officials said Thursday.
States reporting vaccination data noted an 85 percent drop in the highly contagious disease between 2005-2006 and 2013-2014, according to a report from the U.S. Centers for Disease Control and Prevention.
The fall-off was greatest among kids aged 5 to 14, health officials said. This is also the age group most likely to have received the second dose of varicella vaccine.
Symptoms of chickenpox include an itchy, blistery rash, tiredness and fever. It tends to be more serious in babies, adults and people with a weakened immune system, the CDC noted.
Before vaccination, chickenpox was commonplace, with 4 million Americans on average getting the virus annually in the early 1990s. Of those, as many as 13,500 were hospitalized, and 100 to 150 died in a given year, according to the CDC report.
The CDC has credited vaccination with preventing more than 3.5 million cases of chickenpox, 9,000 hospitalizations, and 100 deaths each year.
The vaccine doesn’t prevent chickenpox in everyone, but when cases do occur in people who’ve received the vaccine, the disease is usually milder than it is in unvaccinated people, the report said. For instance, people who’ve been vaccinated tend to have fewer lesions.
Now, with fewer cases to monitor, state health officials can better study the characteristics of new outbreaks — such as symptom severity, the number of hospitalizations and whether or not patients were vaccinated, the agency said.
Scientists say it’s essential to understand why severe cases still occur and whether they occur among vaccinated people.
“Further reduction in the number of varicella cases will provide states with increased opportunities for enhancing varicella surveillance and improving completeness of reporting to monitor impact of the vaccination program,” study corresponding author Adriana Lopez and colleagues wrote.
When the single-dose vaccine was launched in the United States in 1996, a 90 percent decline in cases followed over the next 10 years. But, because of continued outbreaks, the CDC implemented the two-dose schedule starting in 2006.
The CDC recommends kids get the first dose at age 12-to-15 months and the second dose when they are 4 to 6 years old.
By 2014, 40 states were reporting data on chickenpox. Just four — Illinois, Michigan, Texas and West Virginia — have been submitting data annually since before the varicella vaccination program began.
The report was published in the CDC’s Sept. 2 issue of the Morbidity and Mortality Weekly Report.
Reuters Health) – Parents who delay or skip childhood vaccinations even when kids have no medical reason to avoid their shots are contributing to U.S. outbreaks of measles and pertussis, a research review suggests.
More than half of 1,416 measles cases reported in the U.S. since the disease was declared eliminated in 2000 were for people with no history of measles vaccination, the analysis found.
Among more than 10,000 pertussis patients with known vaccination status, 24 to 45 percent of people in the five largest statewide epidemics since 1977 were unvaccinated or only partially vaccinated, the analysis also found.
“If there are a high number of susceptible or unvaccinated individuals in the community the risk of getting infected – even for vaccinated children – goes up,” said senior study author Dr. Omer Saad, a pediatrics and epidemiology researcher at Emory University in Atlanta.
That’s because few vaccines are 100 percent effective, Saad added by email.
With pertussis, or whooping cough, up to 2 percent of people who receive all five recommended vaccine doses on time may still get this bacterial infection of the lungs, according to the U.S. Centers for Disease Control and Prevention.
For measles, roughly 3 percent of people who receive both recommended doses of the vaccine may still get the virus, according to the CDC.
These numbers are a best case scenario, assuming that only people with medical reasons – like certain cancer treatments, rare allergies to vaccine ingredients, or diseases that compromise the immune system – forgo inoculations.
But the CDC reports that fewer than 1 percent of kids need to skip vaccines for medical reasons, based on data from Mississippi and West Virginia, states that only grant exemptions under these circumstances.
Instead, Saad and colleagues found that the majority of measles and pertussis cases in the outbreaks they analyzed were due to people intentionally skipping vaccinations.
Among 970 measles cases with detailed vaccination data, 574 cases were unvaccinated people who were eligible to receive their shots, researchers report in the Journal of the American Medical Association.
Most of these unvaccinated people – 405 of them – had nonmedical reasons for skipping vaccinations such as religious or philosophical objections, the analysis found.
For the subset of pertussis reports from outbreaks with detailed data on unvaccinated individuals, 59 to 93 percent of cases were for people who intentionally skipped their inoculations, the analysis also found.
Several pertussis cases also cropped up in highly vaccinated communities, suggesting waning immunity against the disease, the researchers note.
Limitations of the study include a focus on measles and pertussis in the context of vaccine exemption rates, which may have underestimated the disease risk associated with skipping vaccines, the authors point out.
Nonmedical exemptions also don’t explain all of the resurgence in measles and pertussis in recent years, Dr. Matthew Davis, a pediatrics researcher and deputy director of the Institute for Healthcare Policy and Innovation at the University of Michigan in Ann Arbor, noted in an editorial.
“It is very difficult to put a specific number on how much vaccine refusals reduce a community’s protection against disease,” Davis said by email.
“What this latest comprehensive review illustrates is that individuals who refuse vaccines not only put themselves at risk for disease,” Davis added. “It turns out that they also put others at risk too – even people who have been vaccinated before, but whose protection from those vaccinations may not be as strong as it used to be.”