How to find information: A Step-By-Step Demonstration
Suppose you want to find out what kinds of kids are included in vaccine clinical trials evaluating vaccine safety and effectiveness. Is it an accurate representation of the population of kids that will be receiving the vaccines? What was used as the placebo?
One option for finding this information is going over to clinicaltrials.gov and using their search function. If you were wondering about Prevnar, you’d want to use the search words:
pneumococcal conjugate vaccine safety
That search takes you here. The second study down is this one, an evaluation of the “new” (13 valent)Prevnar that will soon be released, where you can see that the “placebo” is the “original Prevnar”, and the “inclusion and exclusion criteria” for the study are described as:
- Healthy 2-month-old infants.
- Available for the entire study period.
- Previous vaccination with any vaccine before the start of the study.
Known contraindication to vaccination.
Since the placebo being used is a different version of Prevnar, you then might wonder what the trials were like for the “original” version of the vaccine. Now you need to jump over to Google Scholar to search for older trials, and using the keywords “randomized controlled” with the name of the vaccine (pneumococcal conjugate vaccine) as your search terms. Do that, and this is where you will end up. The first study listed is a dead end, but the second one, when you click the “all of X versions” button, takes you here, and when you click through the options you find that the second to last one listed is this, a full-text version of the article.
In addition to finding that the placebo used in this trial was a meningococcal type C conjugate vaccine (an experimental vaccine) you find that that the inclusion/exclusion criteria was defined like this:
Healthy infants were randomized 1:1 to receive either the heptavalent pneumococcal conjugate or the meningococcus type C conjugate vaccine at 2, 4, 6, and 12 to 15 months of age. Children with sickle-cell disease, known immunodeficiency, any serious chronic or progressive disease, a history of seizures, or a history of either pneumococcal or meningococcal disease were excluded.
Here’s another example of how to find information that might be relevant to your vaccine decision-making process.
Suppose you wanted to find out what pertussis infection is like in unvaccinated babies and kids. To find out what kind of keywords to search Google Scholar for, you might want to first try a search with something like this if you’re starting from scratch:
(emedicine is good for finding out what the medical terms are)
So the first emedicine article is this:
Which says this:
The criterion standard for diagnosis of pertussis is isolation of B pertussis in culture.
Obtain the culture specimen by performing deep nasopharyngeal aspiration or holding a flexible swab (Dacron or calcium alginate) in the patient’s posterior nasopharynx for 15-30 seconds or until a cough is produced.
So that would inspire the search term “nasopharyngeal specimen”.
Additional terms like “pertussis, unvaccinated, infant, cough, duration, surveillance” would be other logical choices for your search if you’re wondering about the duration of a cough in unvaccinated infants. You’d also want to look for a “surveillance” study so you didn’t just find the stats on the worst-case scenarios (since the properly diagnosed cases are usually the worst of the worst, and “scientists” have to go out specifically looking for the milder cases with “surveillance studies” to get a “true” picture of disease severity.)
Now, moving over to Google Scholar, trying with keywords:
nasopharyngeal specimens pertussis cough duration unvaccinated infants surveillance
….Entered into Google Scholar, you get this:
Where you find:
The data collected in this study allow a precise description of selected aspects of pertussis as they occur in unvaccinated children. Clinical characteristics of the cough episodes were obtained at two time points: on the day the NPS was taken and 6 to 8 weeks later. At the time of the first assessment, 82.4% of patients had paroxysmal cough, and the majority also had posttussive vomiting, whereas only 5.7% had fever 38°C. In spite of the high prevalence of paroxysmal cough and posttussive vomiting, almost half of the patients were not initially considered to be probably or definitely pertussis by the treating physicians.
This looks like the odds of having complications, should an unvaccinated infant under 6 months old catch it:
Complications were observed in 95 of 1640 (5.8%) patients (Table 2). They were significantly more frequent in infants <6 months of age than in patients >6 months of age (23.8% vs 5.1%; P < .001). Most common complications were pneumonia (29.5%) and apnea (12.6%). Of all infants 6 months of age, 3.2% and 15.9% were reported to have pneumonia and apnea, compared with 1.6% and 0.1% in patients >6 months of age, respectively. There were no seizures reported in this study;
So three fourths of the time, if your baby under 6 months catches it, you still won’t have complications. Other interesting factoids from the study:
From October 1990 to September 1996, 20 972 specimens were submitted, and B pertussis was isolated in 2592 instances (12.4%).
Of the culture-proven cases, 50.7% were female, and the age range was 6 days to 41 years, with a mean and median of 4.3 years and 4.1 years,
So there’s a 50% probability that an unvaccinated child will catch pertussis by age 4. Around age 4 is the average age of infection.
And the severity in the unvaccinated:
Of unvaccinated patients, 90.2% had paroxysmal cough, 78.9% demonstrated whooping, and 53.3% presented with posttussive vomiting; 5.7% had fever 38°C. The duration of cough was 4 weeks in 37.9% and 3 weeks in 17.4%
90.2% had paroxysmal cough
…means one in 10 unvaccinated kids don’t get “the cough” at all when they catch pertussis. A few kids get REALLY lucky.