We are in the midst of one of the largest measles outbreaks in decades, in large part due to multiple pockets of communities refusing vaccination for their children. We are also in the midst of flu season, where thousands have developed complications, and many have died, also in large part due to absence of vaccination. Despite countless large studies demonstrating that vaccination is safe and effective, anti-vaccination rhetoric continues to contaminate online communities, leading to deadly outbreaks of vaccine-preventable diseases.
If an individual receives a measles vaccine between ages 12 and 15 months, followed by a booster shot at age 5 years, the likelihood of the vaccine being effective, meaning that even if exposed to measles one is immune, is greater than 98%. If an individual received a flu vaccine this season, the effectiveness is closer to 50-60%, but flu cases in those who were immunized will be much milder than those who have not been immunized. All of the deaths and complicated flu cases have been in un-vaccinated people (and no, as of this writing, it is NOT too late to get a flu shot for the 2018-19 season). All of the measles cases (and deaths) have been in people not immunized against measles. The math here is pretty simple.
It gets a little more complicated when it comes to a shot to prevent whooping cough, also known as pertussis. This vaccine is given as part of the DTaP (diphtheria, tetanus, pertussis) series, beginning at 2, 4, and 6 months, and later at 15-18 months, and again at age 4-6 years. At age 11-12 years, the Centers for Disease Control recommends a similar vaccine booster, known as Tdap. This vaccine is also recommended during the third trimester of pregnancy, which protects the mother as well as the infant in the first few months of life. Even though the first vaccine is given at age 2 months, immunity to pertussis usually takes two to three boosters prior to the baby being protected against pertussis infection. Prior to availability of the vaccine in the 1940's, approximately 200,000 children contracted pertussis each year, and 90,000 would die of the disease.
Pertussis infection, or 'whooping cough', is caused by the bacterium bordatella pertussis. Babies who contract the illness are more likely to die than older children or adults, as infants and toddlers are unable to clear their air passages from the thick mucus that forms from the infection. In older children, teens, and adults, it's more classically an illness with a 'whoop' sound to the nasty, painful cough. Some cases are mild, and may even seem like a bad cold. Others can last up to 100 days, occasionally landing the 'whooper' in the hospital.
In 2014, Los Angeles, among other major U.S. cities saw a resurgence of whooping cough. Deeper investigation tied these outbreaks to remarkably low vaccination rates, with some schools, both private and public, clocking in with 20% of kindergartners fully immunized on schedule. In 2014, the state of California reported 8,000 cases of pertussis. In the following years, the state removed the Personal Belief Exemption on vaccines, meaning that families wishing not to keep their kids up to date on vaccines would only be able to enter kindergarten with a medical exemption. This helped raise vaccination rates, although medical exemptions then became easy to obtain by physicians willing to sign them.
And now whooping cough is back. In Los Angeles, to start. While only 30 students from one particular school have been reported to have the illness, and all are over the age of 11 years, this relatively contained outbreak may start to spread far and wide. It is likely (although there is no available data on these individuals) that many of the children with the disease are, indeed, up to date with pertussis immunization.
Unlike the measles vaccine, the DTaP and Tdap vaccines are closer to 80-90% effective, even after receiving all five doses. This is why herd immunity is so critical for an illness such as pertussis. Herd immunity is the mechanism that protects large communities of people from vaccine-preventable illness if a 'herd' of people (>95% of a population) are immunized. This allows for protection for those who CANNOT (not will not) be immunized-- those with immune system disorders, those receiving medications such as chemotherapy, infants, and those with active illnesses precluding vaccination. But if the herd is not robust, these illnesses sneak back in, especially for those illnesses (such as pertussis and flu) where the vaccine is not as effective as the measles vaccine. And as with most respiratory illnesses, whooping cough is quite contagious, via coughing, sneezing, or any air droplet exposure. If there is concern that an individual has pertussis, they should be removed from a school or work setting. A primary care physician can perform a culture for diagnosis. Until a negative culture is received, the "whooper" should stay home.
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