Tag: Herd Immunity

I’ve gotten my Covid vaccinations. I’m all immunized. How ’bout you? When are you planning on getting your shots?

As I’m writing this post the number of Covid-19 vaccines that have been administered is here in the United States is 218,947,643. President Biden’s initial pledge of 100 million shots in his first 100 days in office has been more than doubled and even his updated pledge of 200 million in 100 days is a safe bet to be exceeded by more than 10%.

As President-elect Joe Biden pledged to administer 100 million vaccine shots into American arms in his first 100 days as President. He ended up more than doubling that goal. (Credit: New York Post)

27.1% of all Americans have now been fully immunized while more than 50% have had at least their first shot. Over the last month an average of about 3 million people per day have received a shot and all Americans over the age of 16 have now been declared eligible to receive their shots. (All of these statistics are courtesy of the Center for Disease Control CDC.)

The drive to get people vaccinated is one of the largest peacetime efforts ever undertaking by federal, state and local governments. (Credit: Beaumont Health)

All of that means that we are reaching a critical turning point in our war against a disease that in only a single year has killed more Americans than any of our wars except the civil war. 570,611 Americans have lost their lives to Covid-19 and 31,950,831, nearly one tenth of our country’s population have been sickened according the Johns Hopkins University Covid-19 resource center.

At its peak the covid pandemic death toll was so high that makeshift morgues had to be used to store all of the dead! (Credit: The New York Times)

If we can only continue to vaccinate people at our current pace we will almost certainly reach ‘herd immunity’ within another month or two. Such an achievement will mean that by mid summer the US can begin to really open up. Restaurants, movie theaters, sporting events, all of the industries that have suffered enormously because of the pandemic will be able to resume near normal operations. Our economy, which has recently shown signs that it is ready, even anxious to get back to business will be able to do just that. Simply put we’ll be able to get our lives back.

Contagious diseases need a lot of potential victims in order to spread. When the majority of a population gets vaccinated the disease is unable to take hold and spread. (Credit: Wikipedia)

There is a bit of bad news mixed in with the good. There have been cases identified of people who have received their vaccinations and nevertheless later tested positive for covid. That’s actually to be expected, during testing that efficacy of the Pfizer and Moderna vaccines were measured at 95%, which is really good, but still means that 5% of those vaccinated could still get the disease. Even so to date no one who has come down with covid after being vaccinated has become seriously ill or required hospitalization. In other words the vaccines not only do a great job at preventing covid, they virtually eliminate serious cases of the disease.

Some of the vaccines developed to combat Covid are very efficient but none are perfect. (Credit: Statista)

Of course the worst news are those cases of blood clots that have developed in a few people who have received the Johnson and Johnson vaccine. The latest information is that 15 people, all women to my knowledge, have shown symptoms of serious blood clotting after receiving the J&J vaccine and one death has occurred. That number of cases is out of the over 8 million people who have received the single shot J&J vaccine so obviously the incidence of blood clots is very rare. Nevertheless the situation was serious enough that the Food and Drug Administration ordered a pause in the administration of the J&J vaccine while the incidents were investigated. After eleven days of data collecting and analysis of the data both the FDA and CDC decided that the benefits of the vaccine far outweighed the potential risks and lifted the pause while adding a warning to women under 50 informing them of the risk of blood clots.

There is evidence for both the Johnson and Johnson and Astrazeneca vaccines causing blood clots, but there is a greater risk of blood clots from taking birth control pills and even worse for smoking! (Credit: Hindustan Times)

After all consider the odds. Out of about 330 million people living in the US more than 31 million have now gotten covid, that’s nearly a 10% chance of getting the disease and more than half a million have died, a 0.17% chance. On the other hand your chance of getting a serious blood clot from the J&J vaccine is .000188% far, far less likely than the risk due to covid. In fact right now about 700 Americans are still dying every day because of covid while only 15 people have gotten sick because of the J&J vaccine. And remember no deaths thus far have been linked to the Pfizer and Moderna vaccines.

So it’s difficult to understand why so many people are still hesitant about getting vaccinated. In fact current polling data suggest that approximately 17% of Americans only plan on getting vaccinated if it’s required while a further 8% refuse to get vaccinated under any circumstances. These numbers are so large that they could pose a risk to the effort to achieve herd immunity.

According to polls vaccine hesitancy is falling as more and more people get inoculated. We need everyone to realize the benefit of immunization however! (Credit: Statista)

Now there have always been people whose fear of having substances they don’t understand directly injected into their bodies makes them resolute ‘antivaxxers’. Then you can add those people who devoutly believe that faith in god is the only healthcare system they need. Finally in our nation’s current political climate we have many people whose distrust of authority has led them to proclaim ‘their right as Americans to not get vaccinated’. As if the freedom to ignore the deaths of a half million of their fellow citizens is somehow enshrined in the Constitution.

If only it were that easy. (Credit: Henry Kotula)

Remember, covid is a virus; it is incapable of understanding ‘liberty’ in any sense of the word. It is neither a democrat nor republican, neither a liberal nor conservative. It is just going to try to infect you and maybe kill you, that’s all it knows how to do! Face facts, you can’t fight a virus with an assault rifle, nor is this just a left wing plot to destroy conservative American culture. Covid is a disease that is presently out of control and vaccines are our best weapon against it!

Sensible people know this, and know how to analyse risk versus reward. (Credit: SBS)

I’m not going to try to argue with those who will never listen. All I can do is to relate my own medical history as testimony. My parents had our whole family inoculated against polio as soon as the vaccines became available. When I joined the US Navy I was vaccinated I don’t know how many times. I’ve been vaccinated against tetanus, shingles, etc, etc, and I get a flu shot every year. None, I repeat none of those vaccines, including the Pfizer covid vaccine I just received my second dose of, have ever done me the slightest harm.

My vaccination card for the Pfizer Covid-19 vaccine! I’m now all immunized, I can get back to my life…What ’bout you! (Credit: R. A. Lawler)

In fact since the vaccines against Measles, Mumps and Rubella weren’t developed until after I had all those diseases Mumps left me with permanent deafness in my right ear! What I wouldn’t give to have been able to take the MMR vaccine, which you’ll recall is falsely alleged to cause autism, and still have my hearing! So if you’re thinking about getting vaccinated but are hesitant please think of the risks. Over a half a million Americans have died because of covid and maybe one person has died because of a vaccine. Repeat that simple fact about ten times AND GO GET VACCINATED!!!

Social Distancing, Herd Immunity, and R-naught, just a few of the concepts developed by the science of Epidemiology.

With the Covid-19 virus continuing to spread, causing an ever growing number of illnesses and deaths across our planet the science of epidemiology has gone from being a little known branch of medicine to arguably becoming the most vital topic in the world. Literally ‘the study of what is on or among the people’ epidemiology was once the most successful branch of medicine, helping to eliminate such deadly diseases as cholera, typhus and yellow fever. Indeed the doctors and scientists who developed epidemiology succeeded in controlling many infectious diseases without any kind of a cure or in some cases having the slightest idea as to what was causing the illness.

It’s all Greek to me! (Credit: Pinterest)

The ancient Greeks recognized that while some diseases could spread from person to person throughout a population, other illnesses like epilepsy or cancer were not infectious. It wasn’t until 1543 however that an Italian doctor named Girolamo Fracastoro speculated that diseases could be spread by living particles too small to be seen that floated through the air. The invention of the microscope and the discovery that there actually were microscopic living creatures lent considerable weight to Fracastoro’s theory.

Fracastoro and a few other early researchers into the germ theory of disease. (Credit: Open Texbooks)

About a hundred years later in 1662 a part time mathematician, his day job was haberdasher, named John Graunt performed a statistical analysis of the mortality rolls of the city of London before and after the great plague of 1665-66. Graunt’s work provided much evidence supporting some theories about the spread of infection while at the same time disproving others and it established the use of mathematics in the study of diseases.

During the 16th and 17th centuries the city of London had so many plagues that the one of 1665 -1666 is know as ‘The Great Plague’. (Credit: The Lost City of London)

Another Londoner named John Snow became known as the father of modern epidemiology thanks to his work in 1854 leading to his discovering the cause of a number of cholera outbreaks striking the Soho section of London every few years. By simply marking the home addresses of cholera victims on a street map of London, see map below, Snow correctly concluded that the source of the infection was a water pump located on broad street. By disinfecting the water with chlorine and removing the pump’s handle Snow succeeded in ending the outbreak.

John Snow and his map of the distribution of cholera in London.(Credit: The Vintage News)

Another early pioneer was the Hungarian doctor Ignaz Semmelweis who dramatically reduced the infant mortality rate at his Viennese hospital by insisting on rules that promoted cleanliness. Then in the first decade of the 20th century Walter Reed achieved great success in fighting yellow fever in Cuba not by curing his patients who had contracted the deadly disease but by eradicating the mosquitoes who carried the disease from person to person.

Comic book describing how Walter Reed discovered it was mosquitoes that transmitted yellow fever. Yes they used to print comic books about real superheros! (Credit: news.hsl.virginia.edu)

You get the point; the purpose of epidemiology is not to treat the sick but instead to stop the spread of a disease in order to keep other people from becoming sick! That means that often times great advances in epidemiology are made by mathematicians rather than physicians. It has also allowed epidemiology to become the technique used to study social diseases such as obesity, deaths caused by smoking and even gun violence.

The science of Epidemiology being used to study homicides in the city of Detroit. (Credit: Alex B. Hill)

Right now of course the lessons learned from epidemiology are the only weapons we have with which to fight the viral disease Covid-19. Until we have either a vaccine or some really effective anti-viral drug all that each of us can do to protect ourselves is to practice the guidelines developed by epidemiology.

With that in mind it would be a good idea for all of us to understand some of the technical concepts that epidemiologists use to understand how a disease spreads and how we can reduce and control that spread. Probably the factor that is most important in determining, and controlling the spread of a disease is known as its Basic Reproduction Number oftentimes referred to as R-naught or just R0.

Simply put, for each person who becomes infected with a disease, R-naught is the average number of healthy people they will in turn infect. In others words, if you catch a cold and become infectious, R-naught is the number of members of your family, or your co-workers or just people you come into contact with that will catch a cold from you. This also means that if R0 for a disease is greater than one, then the number of people infected is going to grow. For example if R0 for a disease is two then one person will infect two people, those two will go on to infect four and the four will infect eight and so on until almost everyone has, or has had the disease.

A small change in R-naught, say from 2 to 3, can make a huge difference in the number of infected people in a very short period of time. (Credit: University of Scranton)

Under normal conditions in human society there are many diseases that have an R0 much greater than one.  The table below shows the estimated R0 numbers for some well-known diseases.

Table of R-naught for several well known diseases. (Credit: Wikipedia)

Obviously the goal of epidemiology is to find methods and procedures that a community can take that will reduce R-naught for a disease below one. Perhaps the simplest technique is called ‘Social Distancing’ and it just means having everyone in a community reduce the amount of contact that they have with everyone else. No shaking hands when you meet someone, no hugs for friends you haven’t seen in years, also no parties and no big crowds at sports events or concerts. Social distancing works because less contact between people makes it less likely that a germ will pass between them.

Some of the rules of Social Distancing. (Credit: Orange County N. C.)

Looking back at the table you can see how many diseases spread through particles or droplets in the air. Those particles can only travel through the air for about three or four meters so if everyone stayed more than four meters apart those diseases could not spread. R0 would go very close to zero.

Of course such extreme social distancing is not really possible, we live in families and the jobs of many people are so essential that society cannot get along without them. We live in a society and that society requires a certain amount of contact between its members. That’s why other procedures, such as washing hands, disinfecting everything other people touch, and wearing face masks become so important. In fact anything that we can do to reduce R-naught is important, it is at present the only way we have to fight Covid-19. 

Now for many viral diseases those people who are infected and recover acquire an amount of immunity to being re-infected. In such cases, once a majority of the population has been infected the spread of the disease is inhibited because there are now fewer victims left to infect. Not only that but actually the people who have become immune get in the disease’s way, getting between those who are infectious and those who have not yet been infected, effectively generating a macabre form of social distancing. This acquired immunity of the majority of a population is known as ‘Herd Immunity’.Herd immunity should be considered the last resort in fighting a disease however because it results in the maximum number of deaths and hospitalizations of sick people. Basically getting to herd immunity means not fighting a disease and just letting people get infected.

Herd Immunity without a vaccine, top. With a few people getting a vaccine, middle and with a large majority getting a vaccine. Which do you prefer? (Credit: Wikipedia)

Surprisingly there are many people who believe that is the best solution to Covid-19. Indeed the entire nation of Sweden has decided to forego all social distancing measures and just let the disease die out on its own.

One last point, when and if a vaccine is developed that is effective against Covid-19 it will grant immunity to people who have not yet been infected by the disease. In epidemiological terms a vaccine therefore works by getting a population to herd immunity without people dying or being admitting to a hospital, without them getting sick at all. Something I’m certain that we are all looking forward to!