Editor's Note: (Kent Sepkowitz is a CNN medical analyst and a physician and infection control expert at Memorial Sloan Kettering Cancer Center in New York. The views expressed in this commentary are his own. View more opinion at CNN.)
(CNN) Weeks after the US Food and Drug Administration authorized the Pfizer vaccine for adolescents, the United States hit a crucial milestone: More than half of the US population age 12 and older is now fully vaccinated..
While this was a remarkable accomplishment, it was actually the easy part. The next challenge in the US vaccination program is a real doozy: vaccinating little kids.
The crux of the problem is this: Do we really want to inject an entire generation of cute toddlers and grade schoolers at varying stages of immune maturity with messenger RNA -- a strand of genetic code that instructs cells in the body to make a particular piece of the virus' spike protein -- in order to prompt the immune system to mount an intense response?
Well, um, sure, of course ... I'm all in. But let's be honest -- even the most vaccine-enthused among us (me, for instance) gets a bit wobbly at the knees at the thought. As a parent, my instinct is to worry, then worry some more -- but as an infectious disease specialist, I have come to trust the process.
For many, the idea of performing a clinical trial in children before they are able to speak or indicate symptoms may seem concerning; however, this is business as usual in the world of vaccinology. In the past, many vaccine studies were performed predominantly in children since they are the ones at highest risk for diseases such as polio, measles and chickenpox. Thus, the methods, including how to assure informed consent, how to follow up (drawing blood can be no easy task in a 3-year-old), and how to monitor long-term safety, have been worked out.
The reasons to vaccinate against Covid-19 are also compelling. First, though children usually have mild cases, sometimes they get very sick. Earlier this month, the US Centers for Disease Control and Prevention (CDC) reported that hospitalization rates for Covid-19 among a slightly older group of children -- between the ages of 12 and 17 -- were more than double that for influenza in the past three years. Preventing infection in this group will ultimately prevent hospitalizations.
Then there is the public good vaccination will provide as we struggle toward herd protection. In the United States, there are about 50 million people 11 years old and younger, representing 15% of the total population. Though children are not substantial transmitters at home or in schools, vaccinating them will help move us closer to a normal-ish life.
To overcome the collective concern and move the discussion from free-floating parental worry to real information, clinical trials of the Pfizer/BioNTech and Moderna vaccines in children from 11 to as young as 6 months opened in March of this year.
The studies are similar: About 4,500 children in the Pfizer/BioNTech study and 7,000 in the Moderna trial will receive the familiar two-shot series and then be followed for months. The placebo-controlled trials will examine three different dosages to identify the optimal vaccine strength in each of three age groups. The study will determine rates of acute Covid-19 infection, levels of antibodies, as well as short- and long-term side effects.
Formal documents available indicate the trials should close next spring (2022) with fully analyzed results in 2023. However, leaders at Pfizer/BioNTech and Moderna have suggested useable results may be available by autumn 2021, particularly in the 5-to-11 age group.
Even with these results, the Pfizer/BioNTech and Moderna vaccines introduce additional unease because they use messenger RNA technology, a novel approach to vaccines that has not previously been used in humans. In the 1980s, there was a similar excitement and apprehension when the first genetically manipulated injections, called "recombinant" vaccines, were introduced to prevent hepatitis B. (These also may be referred to as "recombinant DNA" or "recombinant protein" vaccines and have successfully been developed against other infections.)
To make a recombinant vaccine, a specific snippet of genetic material from the target virus (such as hepatitis B) is spliced into a living bacteria or yeast. Next, the bacteria or yeast is reprogrammed and directed to make millions of copies of the snippet that had been spliced in. Finally, after some high-tech processing, these little copies of the target virus snippet are injected into a person, inducing immunity. The recombinant vaccines -- which use just a snippet of the virus, rather than the entirety of a weakened or inactive one -- is in some ways a precursor of mRNA vaccines.
In the 1970s, the idea of scientists working with DNA, much less injecting bits of it into people, was met by some serious resistance. People were concerned that scientists were playing with the building blocks of life and that the consequences could not be predicted. A more specific worry was that the vaccine might, by provoking the immune system, cause inflammatory conditions.
Early on, researchers studied whether the recombinant hepatitis B vaccine was indeed causing an increase in cases of multiple sclerosis, an autoimmune disorder. The concern was eventually allayed by analyzing large population-based data sets that revealed no causal association.
Though the CDC and other authorities determined the vaccine to be safe, there are still concerns about this link. A provocative report from the United Kingdom in 2004 -- nearly two decades after introduction of the hepatitis B vaccine -- again suggested a link. Follow-up articles as recently as 2020 that analyze the presented data continue to refute it.
The mRNA vaccinations against Covid-19 are likely to cause a similar back and forth that also may stretch across the decades as experts and concerned consumers debate safety. Vaccine advisers to the CDC have said the number of cases of myocarditis, an inflammation of the heart, and pericarditis, inflammation of the heart lining, has been higher than expected among young people, most often males. Thankfully, the incidents are rare (the CDC researchers estimate there might be 56 to 69 cases of myocarditis for every 1 million second-dose vaccinations) and most cases are mild with symptoms that clear up quickly.
It's important to note that myocarditis and pericarditis have been linked to another vaccine that did not use the mRMA technology -- the smallpox injection used in the early 2000's for young military personnel.
Some of these adverse events in Covid-19 vaccine recipients were detected after study participants were more thoroughly evaluated, and the government operates a national reporting system that monitors the safety of vaccines years after they are introduced.
Though arduous and at times hair-raising, this type of check and re-check and re-re-check, along with carefully performed clinical trials that examine possible early side effects, are the foundation of any worthy safety program. Still, there remains the unalterable fact that as with every scientific breakthrough, we are venturing into new territory.
Which gets us back to what to do about vaccinating small children. The answer is simple: Do whatever the data shows. Actual information, not advice from computer models or experts or the newest talking heads, is forthcoming -- maybe in the fall, maybe later. If the clinical trials in younger children determine the benefits of the vaccines outweigh the potential dangers, we should administer them. And if not, we should hold back on doing so.
So let's wait and see. At times, the rational, evidence-based world can be a tough place to live -- but it sure beats the alternative. And as we wait for the information, it is a great time to focus on achieving widespread vaccination of those 12 to 17 years old.