THE SCIENCE BEHIND LIFE-SAVING VACCINES

So when did it all begin?  In 1796, an English doctor Edward Jenner, infected an eight-year old boy with a small amount of cowpox pus.  Cowpox was similar to smallpox but much less dangerous.  Many people were horrified at Jenner’s work, but the boy later proved to be immune to smallpox which back then was claiming the lives of around 400,000 people a year in Europe alone.  Jenner realized that milkmaids who had caught cowpox were subsequently immune to smallpox.  He came up with the word vaccine from “vacca”, the Latin word for cow.  In 1979, the World Health Organization (WHO) declared that smallpox had finally been wiped out.  

One hundred years later, a French chemist Louis Pasteur made the next major breakthrough.  In 1885, a young boy suffering from rabies arrived at Pasteur’s lab close to death.  Pasteur had been experimenting with turning a weakened form of rabies into a vaccine, and gave the boy a series of injections.  The boy regained full health, Pasteur went on to vaccinate thousands of people, and today many vaccines are still made using his methods.  Swiss-born doctor Alexander Yersin created a vaccine against Diphtheria and in 1894 discovered the Yersinia pestis bacteria that caused Bubonic Plaque.  Improved sanitation and hygiene, rodent control, and the development of antibiotics drastically reduced the number of deaths from this disease.

Today through vaccines, we are protected against many potentially debilitating diseases and once-common killers including: measles, mumps, rubella, diphtheria, tetanus, pertussis (whooping cough), hepatitis A, hepatitis B, human papilloma virus, influenza, Covid-19, pneumococcal disease, meningococcal disease, rotavirus, and typhoid fever.  These vaccines are critical public health tools and are essential for maintaining herd immunity and preventing outbreaks.  The US was declared measles-free in 2,000.  As of April 10th 2025, the Center for Disease Control (CDC) has reported 720 confirmed cases across 25 different US states and there have been 2 confirmed deaths.  The vaccination status of 97% of cases is either unvaccinated or unknown.  

Measles is very contagious for several reasons:

1. It is caused by an airborne virus which is transmitted through respiratory droplets when an infected person coughs or sneezes.  Even if the infected person is not in the vicinity, the virus can remain stable in the air and on surfaces for up to two hours, increasing the likelihood of transmission.

2. The basic reproduction number for measles is high at 12 to 18.  This means that one infected person can spread the virus to 12 to 18 other people in an at-risk population.

3. The signs and symptoms of measles start appearing 1 week after a person is infected so they can spread it to others when they don’t even know they are contagious.

4. Measles can spread rapidly in populations with low immunization rates.

   
   

High levels of vaccination within a population are necessary to ensure herd immunity which protects those who are unvaccinated.  When vaccination rates drop, the risk of an outbreak increases significantly due to easy transmission of the virus among susceptible individuals. 

So what’s the big deal about measles?  Well, it can cause some serious complications like pneumonia, encephalitis (infection of the brain), rarely blindness, and a chronic debilitating inflammatory condition of the brain; subacute sclerosing encephalitis, 7 to 10 years after the primary infection.  Initial measles symptoms include high fever, and cold-like symptoms; cough, runny nose, and watery eyes 7-14 days after infection.  The measles rash begins 3-5 days after the cold symptoms. The rash starts at the hairline, then spreads downward, to the face, neck, and trunk. It can cause diarrhea and ear infections as well.

All parents want to do what’s best for their children.  Vaccine hesitancy or opposition  to vaccines can stem from a variety of concerns and beliefs.  Some parents struggle with vaccine information from reputable sources versus conflicting information and myths perpetuated by anti-vaccers on websites, the internet and social media platforms.  Others question the validity of vaccine research clinical trials sponsored by pharmaceutical companies, believed to be motivated by money.  I sometimes hear stories or anecdotes, from vaccine-hesitant parents about a child that experienced something bad after receiving a vaccine.  I have been vaccinating thousands of children for over 25 years and have had only one instance of a serious complication which fortunately resolved fully after 4 weeks.  It was documented as a rare complication of the vaccine in the vaccine information sheet.  It should be noted that when there are high vaccination rates, any negative health outcome in the first two years of life will most likely occur in a vaccinated child.  If a child has something bad to happen to him or her, after receiving a vaccine, it doesn’t mean that the vaccine is the cause.  Determining causal relationships requires scientific inquiry.

Parents should trust their Pediatrician or other health care provider for the truth about vaccines.  I have vaccinated my own child and recommend fully vaccinating your child according to the vaccine schedules approved by the CDC and Amercan Academy of Pediatrics (AAP).  Vaccines are generally safe and are very effective.  Not vaccinating is truly a risk and delaying vaccines leaves a child vulnerable to potentially dangerous pathogens for a longer period of time than necessary.  

Please feel free to email me with any questions that you may have.

Charlene Blache M.D., F.A.A.P.

Charlene.blache@gmail.com