Near the end of last week’s debate among the Republican candidates for the US presidency, CNN’s moderator, Jake Tapper, sought comments from Dr. Ben Carson, Donald Trump and Senator/Dr. Rand Paul regarding anti-vaccination statements Mr. Trump had made previously. Mr. Tapper’s inclusion of this subject after nearly three hours had elapsed in the debate demonstrated that perhaps CNN, in milking record-breaking ratings, had let the event run too long. And had its well of discussion points for presidential contenders run dry? It is tempting to think so.

After all, who expected Mr. Trump to flip-flop in his support for a non-existent link between autism and childhood vaccinations? And did we really have anything to gain from politicians spinning their way through a complex scientific matter? Mr. Trump could be excused somewhat for his populist opinion. At least Dr. Carson got it right in two separate responses when he refuted the connection between autism and vaccination. However, one would have expected him and Dr. Paul not to muff it in their opportunity to support vaccination more vigorously with documented evidence. Instead, they vacillated regarding vaccination as an example of “big government” intrusion into individual freedoms.

These three politicians range from a proponent of progressive, big government to one who is a noted libertarian; it is disappointing that they used vaccination as one clear demonstration that they are on-board their party’s platform declaiming the primacy of individual will. The two doctors could not articulate opinions in line with current research, so it is difficult to imagine that this is the best issue to leave to independent discretion. Internet searches cannot yet supplant the opinion of an informed physician regarding an individual’s health. Perhaps because these two doctors stopped practicing medicine some time ago in specialties other than those at the frontline of childhood vaccination–Dr. Paul was an ophthalmologist and Dr. Carson was a pediatric neurosurgeon–we can forgive their lack of a handy command of the relevant research; however, this also serves as an example that sensible advice can give way to self-justification and political expediency.

Immunization has proven itself as one of the most successful and cost-effective global public health interventions yet, perhaps running second only to the provision of clean water and sanitation. However, vaccination has not received the same universal acceptance as has public water disinfected with chloramines for drinking purposes—er, sorry, one does not have to look very long to uncover some controversy there, as well.


The central thesis of the three candidates is that “too many shots in too short a time” are given to children. What we should be talking about here is the amount of antigen: molecules such as carbohydrates (sugars), lipids (fats), proteins and nucleic acids (DNA or RNA) by themselves or usually in a combined form. These present themselves as components of the cells of the pathogenic organisms which come into contact with essentially our two immune systems: one innate and the other adaptive. Both systems utilize proteins and specialized cells to destroy or consume pathogens, and the adaptive system also creates antibodies to interfere with a pathogen’s cellular function and binding with our cells. The challenge with vaccine development is to discover which antigens associated with a pathogen serve up the best trigger for our immune systems to halt that pathogen’s multiplication within our body.

Interference from maternal antibodies is the principal reason that some vaccines won’t be effective for a newborn in its first several months of life. The immune systems of a newborn are developed well enough to protect him from the invasion of foreign antigenic material from birth onwards and can mount an effective cellular immunity (including killer T cells). Thus, a few vaccines triggering cellular immunity, such as the one directed against hepatitis type B, can be administered shortly after birth. While an infant’s ability to form antibodies (humoral immunity) lags his cellular immunity for the first two years of life, vaccines are carefully developed to work around this imbalance. Recent research has found that there is a great deal of overlap between these two types of adaptive immunity, so the idea that vaccines impede the action of one part of the immune system at the expense of the other is outdated.  

In 1980, children in the US under the age of two received vaccines against seven diseases; today the CDC currently recommends fourteen vaccines. However, we should not rise to Mr. Trump’s conclusion that young children today receive vaccines equivalent to those “meant for a horse”. In the ‘80s, the seven vaccines exposed children to around 3,000 antigen proteins. Today’s fourteen vaccines are better designed and do their work effectively by introducing only 150 antigen proteins in total–over two years. It is important to note that a child’s immune system confronts 2,000-6,000 foreign antigens each day.

To put this into perspective, when we consider the burden a single vaccine containing 100 antigens would place on the available number of cells (B cells) that create antibodies, we find that a child’s immune system could capably handle receiving 10,000 of these vaccines at any one time. If a child were given all fourteen of the currently recommended vaccines all at once, they would tax only 0.1% of the child’s humoral immune system. Finally, vaccines should no longer suffer blame for the reported increases in childhood allergies and development of autoimmune illnesses. Research comparing rates of allergies among children in the US to those of the developing world has brought about a ‘hygiene hypothesis’. This suggests that exposure to worms and parasites, which plagued the US in the past, is largely absent today, and this dearth of stimulation may ‘hyper-sensitize’ portions of the immune systems of US children.

Steven Smith, M.Sc. is an Infectious diseases epidemiologist