flu vaccine

While there will be news stories each flu season about people who die from flu-related causes, there will be no stories about people who die from getting a flu shot. 

Influenza, aka "the flu," is caused by viruses and is recognizable by its effects: fever, aching in the muscles and bones, cough, sore throat, headaches, and fatigue. The flu can cause severe lung inflammation that leads to pneumonia, lung failure, and, in some cases, death. Influenza is highly contagious. Healthy adults may infect other people one day before symptoms develop and up to five to seven days after becoming sick. Symptoms usually start one to four days after the virus enters the body. "People with flu can spread it to others up to about 6 feet away. Most experts think that flu viruses are spread mainly by droplets made when people with flu cough, sneeze, or talk."* You may be infected with the flu virus, have no symptoms and yet pass on the virus to others. It takes about two weeks for the flu vaccine to be effective. Some people with no symptoms of the flu may be infected when they get the vaccine. The vaccine will not protect those who are already infected. Antiviral drugs can lessen the severity of flu symptoms and shorten the time you are sick. They may also prevent serious flu complications.*

The flu vaccine is the best defense against the flu. That we have such a vaccine is a testament to the dedication and intelligence of scientific researchers working under conditions of great uncertainty. There are two main types of viruses (called "A" and "B") that cause the flu in humans and these viruses have many variations ("A", for example, has 27 subtypes). (A third type of flu virus, called "C", causes a mild respiratory illness.) Viruses mutate; vaccines must be adjusted for these mutations. No vaccine can protect against all possible flu viruses. Researchers must evaluate a number of factors in making their decision as to which viruses are likely to be most active and threatening in the next flu season. Scientists cannot wait until the first victims of the season are identified to develop a vaccine for that season. It takes time to produce the vaccine and distribute it.

It may seem that vaccine makers are playing a game of catch-up with viruses that always stay one step ahead by mutating, but this is not completely true. The 2013/2014 flu season vaccine protects against the H1N1 strain that first appeared in 2009, causing the first influenza pandemic since 1918. Most flu deaths occur in infants and those over 65, but the majority of H1N1 deaths occur in those between the ages of 18 and 64. Still, healthy people in the prime of life are dying in 2014 from the H1N1 virus because they or those around them have not been vaccinated. Unfortunately, we are seeing news stories like this one far too often:

Nineteen people have now died from flu complications in Middle Tennessee — a figure that surpasses the number of area residents who perished in the 2009-10 global pandemic, according to hospital data.

In the eight-county area that Vanderbilt University tracks, most of the deaths have been among 41- to 64-year-olds. The predominant strain circulating this year, H1N1, first emerged during the pandemic and typically hits people in the prime of life.

Patrick Sass, 46, described by his family as a strong, healthy outdoorsman, was one of those.*

The H1N1 2009 mutation was atypical of the kind of mutation most flu viruses make. It was an example of antigenic shift, not antigenic drift, which involves minor genetic changes that can still "render new virus strains that may not be recognized by the body's immune system." Vaccine makers are aware of these genetic shifts and drifts and use this information in deciding what strains of virus to protect against next season. There is no perfect flu vaccine and probably never will be.

How effective and safe is the annual flu vaccine? Vaccine effectiveness (VE) varies from year to year, depending on what strains are active and what strains were predicted to be active. VE also depends on who gets vaccinated in a given flu season. For example, if many children don't get vaccinated and the dominant viral strain is especially harmful to children, but not too harmful to adults, then VE will be very low that year even if the experts correctly predicted which viral strains to protect against. If, on the other hand, the dominant strain is H1N1, the experts select that strain to protect against, and there is a very high vaccination rate among those between the ages of 18 and 64, VE will be very high that season. It should be obvious that there cannot, in good conscience, be any randomized control group studies on the effectivenss of flu vaccines. All studies must be observational, making it all the more difficult to accurately assess VE. (See here for an example of some of the problems faced by researchers trying to determine VE in those over 65.)

Effectiveness also depends on such things as the robustness of the immune system of those being vaccinated. Vaccines may not be highly effective for those suffering from chronic illnesses. There may be other individual factors that hinder the effectiveness of flu vaccines in some people. Attempts to quantify the effectiveness of flu vaccines are, in my opinion, misleading because 1) the number of factors to be considered are immense and vary from season to season, as well as from individual to individual; and 2) it is always risky to try to apply a statistic that holds for a large group to any given individual who is part of that group. Still, I am not against trying to quantify VE in principle, but I do recommend caution in using such data as a reason for getting or not getting vaccinated. In any case, the US Centers for Disease Control and Prevention (CDC) estimates VE at 60%, which it describes as meaning that "the flu vaccine reduces a person’s risk of developing flu illness that results in a visit to the doctor’s office or urgent care provider by 60%."

The safety of flu vaccines is indicated by the fact that: "The seasonal flu shot has been given safely to millions of pregnant women over many years. Flu shots have not been shown to cause harm to pregnant women or their babies." In fact, it is highly recommended that pregnant women get a flu shot because they "have a higher risk for serious complications from influenza than non-pregnant women of reproductive age. Influenza vaccine will protect pregnant women, their unborn babies, and protect the baby after birth."* Hundreds of millions of Americans have been vaccinated against the flu without adverse effects, but it is true that there is no way to predict with absolute certainty how any given individual will react to a particular vaccine. Healthcare providers are required by law to report possible adverse side effects from vaccines. The Vaccine Adverse Event Reporting System (VAERS) accepts reports of possible side effects from vaccines. Anyone may report an adverse event that happens after getting a vaccine and such reports are recorded, but it should be noted that some of these events are coincidental. The most common side-effect from vaccinations is soreness at the location of the shot. Most people have no adverse events caused by a flu vaccination. Some children experience a runny nose, wheezing, headache, vomiting, muscle aches, and fever. Some adults experience a runny nose, headache, sore throat, or cough. A small percentage of the population may be allergic to something in the vaccine. "Signs of a serious allergic reaction can include difficulty breathing, hoarseness or wheezing, swelling around the eyes or lips, hives, paleness, weakness, a fast heartbeat, or dizziness....People who have an allergy to eating eggs should discuss flu vaccination with their doctor. Many egg-allergic individuals can safely receive influenza vaccine." While there will be news stories each flu season about people who die from flu-related causes, there will be no stories about people who die from getting a flu shot. (When I posted this article, the flu season for 2013/2014 was about half over and the news report in my state of California was that so far 95 people had died from the flu. No Californian has died from the flu shot. Dr. Gil Chavez, California state epidemiologist, said 80 percent of those who died had not received a flu vaccine.)

While not 100% effective, the flu vaccine is still the best defense against the flu. Anyone 6 months of age and older should get vaccinated, especially pregnant women, unless, of course, you've had an allergic reaction in the past to the flu vaccine or have a chronic illness or compromised immune system.

The CDC said that, of the 3,745 flu-related hospitalizations reported so far [during the 2013/14 season], 61 percent have been in people 18 to 64 years old, a pattern also seen during the 2009 H1N1 pandemic. “Having looked at H1N1, we can tell in fact that it affects younger individuals, and tends to affect the most those with the most severe medical conditions,” Chavez said. He said 80 percent to 90 percent of the cases have been “younger individuals” who also have underlying conditions such as pregnancies, immune-suppressing diseases and obesity. By far, the most dangerous underlying condition nationwide has been obesity in those hospitalized with the flu, with 45 percent of patients reported obese, said Angela Campbell, with the CDC’s Influenza Division. Other risky medical conditions have been metabolic disorders, cardiovascular disease and asthma, particularly in children.*

When one considers the pros and cons of getting the annual flu shot, it seems obvious that the benefits of getting the shot outweigh the risks. There are, however, many stories out there claiming many false things about the dangers of getting a flu shot or the lack of benefit from getting vaccinated. Science journalist Tara Haelle has collected a list of myths about the flu vaccine and has posted them along with her setting the record straight. Last I looked, there were twenty-five myths listed. The CDC also has a web page on Misconceptions About Seasonal Flu and Flu Vaccines. One of the more common misconceptions is that it is better to get the flu than to get the flu shot because getting sick builds up the immune system. "Flu can be a serious disease, particularly among young children, older adults, and people with certain chronic health conditions, such as asthma, heart disease or diabetes. Any flu infection can carry a risk of serious complications, hospitalization or death, even among otherwise healthy children and adults. Therefore, getting vaccinated is a safer choice than risking illness to obtain immune protection."* In any case, getting the flu will not provide you with lifetime immunity from the flu for the same reason that a new flu vaccine is offered annually: antigenic drift and antigenic shift. The antibodies produced by the vaccine may provide protection from specific viruses for about a year. At best, the antibodies produced in fighting off the flu may offer protection from the same virus for another year or two.

The flu vaccine is available either as a shot or as a nasal spray. Which you should get depends on your age and physical condition. Those on long-term aspirin treatment should not use the nasal spray. Ask your health care provider which is best for you. Neither vaccine can give you the flu.

Most flu vaccines are trivalent—designed to protect against three different flu viruses (two A viruses and one B virus), but some are quadrivalent—designed to protect against four viruses (two A viruses and two B viruses). Your health care provider should know which is best for you.

If you are ill, you should not get a flu shot until you recover. If you have a history of Guillain-Barré Syndrome, you should not get a flu shot.

There are many anti-vaccination websites that try to scare people into not getting vaccinated. Some of these sites are based on ignorance or intentional deceit. For example, they will point out correctly that the flu vaccine contains formaldehyde, a known carcinogen. Formaldehyde is used in manufacturing vaccines to kill viruses and bacteria that can cause diseases. The formaldehyde is diluted during the vaccine manufacturing process and only small residual quantities of formaldehyde remain in vaccines. What the vaccine deniers don't tell you is that unusually high or prolonged exposure to formaldehyde may cause cancer. They don't tell you that small amounts of formaldehyde are found in many foods, like apples and pears, which I'm sure many anti-vaxxers feed to their infants in pureed form. They don't tell you that the latest research has shown that the highest risk is from the air when formaldehyde is inhaled from breathing. Nor do they tell you that cancers occur more frequently in people who routinely use formaldehyde in their jobs. There is no evidence linking cancer to infrequent exposure to tiny amounts of formaldehyde via injection as occurs with vaccines. Furthermore:

The body continuously processes formaldehyde, both from what it makes on its own and from what it has been exposed to in the environment. The amount of formaldehyde in a person’s body depends on their weight; babies have lower amounts than adults. Studies have shown that for a newborn of average weight of 6 -8 pounds, the amount of formaldehyde in their body is 50-70 times higher than the upper amount that they could receive from a single dose of a vaccine or from vaccines administered over time.*

The human body manufactures formaldehyde without causing cancer. Formaldehyde is produced naturally in the human body to produce energy and build the basic materials needed for important life processes. "This includes making amino acids, which are the building blocks of proteins that the body needs."

Formaldehyde is a normal, essential human metabolite with a biological half-life of about 1.5 minutes. It is endogenously produced and is involved with methylation reactions for and biosynthesis of some proteins and nucleic acids. It is also rapidly metabolised to formate and excreted in urine or to carbon dioxide and exhaled.*

Another scare tactic by anti-vaccinationists is to warn people that flu vaccines contain aluminum salts (which some anti-vaxxers call "detergent") as an adjuvant, a substance that helps stimulate the body’s response to the antigens. What the anti-vaxxers don't tell you is that "aluminum adjuvant containing vaccines have a demonstrated safety profile of over six decades of use and have only uncommonly been associated with severe local reactions."* (See Polyionic vaccine adjuvants: another look at aluminum salts and polyelectrolytes. Clinical and Experimental Vaccine Research. 2015 Jan;4(1):23-45.)

Another scare tactic used by anti-vaccinationists is to warn people that flu vaccines contain antibiotics. What they don't tell you is that the antibiotics are used during manufacturing to prevent bacterial contamination. Nor do they tell you that the "antibiotics most likely to cause severe allergic reactions (e.g., penicillins, cephalosporins and sulfa drugs) are not used in vaccine production, and therefore are not contained in vaccines."*

Another scare tactic is to warn people that flu vaccines contain sugar and gelatin. What they don't tell you is that these are used "to keep the vaccine potent during transportation and storage." Nor do they tell you that these are not unique to vaccines and are encountered in everyday life in the diet and are components that are in the body naturally.

About the same time as the Andrew Wakefield fiasco, anti-vaxxers began using as their trump card the fear of neurological disorders from mercury in vaccines. Thimerosal, which is metabolized in humans to ethylmercury, has been used since the 1930s as a preservative to prevent contamination by microbes in vaccines. Today,

the only childhood vaccines used routinely in the United States that contain thimerosal are flu vaccines in multi-dose vials. These vials have very tiny amounts of thimerosal as a preservative. This is necessary because each time an individual dose is drawn from a multi-dose vial with a new needle and syringe, there is the potential to contaminate the vial with harmful microbes (toxins).

There is no evidence that the small amounts of thimerosal in flu vaccines causes any harm, except for minor reactions like redness and swelling at the injection site. Although no evidence suggests that there are safety concerns with thimerosal, vaccine manufacturers have stopped using it as a precautionary measure. Flu vaccines that do not contain thimerosal are available (in single dose vials). 

Anti-vaccinationists also claim that the flu vaccine is not effective, but they don't tell you that there is an abundance of scientific evidence that demonstrates that flu vaccines are effective. As the reader can probably surmise, it is not a simple matter to evaluate the vaccine efficacy (VE) of the flu vaccine, given all the variables that go into how the viruses work and how the vaccine must be developed. I've already mentioned that the CDC considers the scientific evidence to support the claim of 60% VE. I've also already explained why I am not a fan of quantification in this area. I might add that quantification opens the door to statistical chicanery by both those who support and oppose vaccines. Anyway, one recent study is worth mentioning: Influenza Illness and Hospitalizations Averted by Influenza Vaccination in the United States, 2005–2011. The scientists provide support for a VE similar to that of the CDC. For those who like extrapolations from numeric data, this translates into 1.1 million to 5 million flu infections prevented during each flu season over six years. An article in The Lancet (Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis) found an even higher VE for children and most adults. One interesting finding was a lack of evidence for protection in adults aged 65 years or older, which supports other research despite the fact that the elderly are particularly vulnerable to death by flu-related causes and are highly targeted by public health officials.* The highest efficacy (83%) was in young children (aged 6 months to 7 years).

Anti-vaccinationists also claim (falsely) that vaccines didn't lead to a decrease of infectious diseases from measles, rubella, mumps, etc. The evidence they present is the irrelevant charting of a decrease in mortality before and after the widespread introduction of vaccines and the assertion that improvements in diet, hygiene, and sanitation account for the decrease in mortality. Suffice it to say here that the issue regarding the effectiveness of vaccines is not the same as the issue of mortality: disease incidence does not equal death. Nobody has ever claimed that vaccines saved the lives of all the people who were ever vaccinated. Anyway, this deceptive anti-vaxxer trope has been thoroughly trashed by David Gorski and there is no need to repeat the arguments here.

Finally, there is no medical condition called "the stomach flu," despite the expression's common usage to describe illnesses with nausea, vomiting, or diarrhea. The flu is a respiratory illness, not a stomach or intestinal disease. The flu is often confused with the common cold, but they are caused by different viruses. There is no vaccine for the common cold.

See also the anti-vaccination movement, Rights and Vaccines, and the nirvana fallacy.

further reading

The Flu Vaccine Is Safer Than We Knew Even for children with egg allergies. By Jessica Martin. Slate.

Even in 2014, Influenza kills by David Gorski, M.D.

Estimating Seasonal Influenza-Associated Deaths in the United States: CDC Study Confirms Variability of Flu "CDC does not know exactly how many people die from seasonal flu each year. There are several reasons for this. First, states are not required to report individual seasonal flu cases or deaths of people older than 18 years of age to CDC. Second, seasonal influenza is infrequently listed on death certificates of people who die from flu-related complications. Third, many seasonal flu-related deaths occur one or two weeks after a person’s initial infection, either because the person may develop a secondary bacterial co-infection (such as bacterial pneumonia) or because seasonal influenza can aggravate an existing chronic illness (such as congestive heart failure or chronic obstructive pulmonary disease). Also, most people who die from seasonal flu-related complications are not tested for flu, or they seek medical care later in their illness when seasonal influenza can no longer be detected from respiratory samples."

H1N1 pandemic death numbers like seasonal flu: Between 62 per cent and 85 per cent of those who died in 2009 pandemic were under 65 "When one uses years of life lost as a measuring stick against which to assess the pandemic, its [the H1N1 pandemic] severity is in line with the 1968 Hong Kong flu, the pandemic which preceded the 2009 outbreak...Michael Osterholm, an infectious diseases expert at the University of Minnesota, agreed years of life lost is a better way to gauge the impact of the 2009 pandemic."

A detailed and thorough review of every claim made in Andrew Wakefield's book about vaccinations concludes: "I have shown that every major claim Wakefield makes in his book concerning vaccine safety is wrong." See "Wrong About Vaccine Safety: A Review of Andrew Wakefield’s “Callous Disregard”" by Joel A. Harrison, PhD, MPH in The Open Vaccine Journal, Vol 6, 2013, pp 9 – 25.

Setting the record straight: Debunking ALL the flu vaccine myths by Tara Haelle "I am a science journalist but not a medical doctor. I’ve compiled research here to debunk common myths about the flu vaccine. You should always consult a reliable, trusted medical professional with questions that pertain specifically to you."

Toxic Myths About Vaccines by David Gorski

Key Facts about Influenza (Flu) & Flu Vaccine - CDC

Vaccine Ingredients - US CDC

Common Ingredients in U.S. Licensed Vaccines - US FDA

Flu Shot and Egg Allergies - The American College of Allergy, Asthma, & Immunology: "In a 2012 study published in the Journal of Allergy and Clinical Immunology, Des Roches et al. combined their data with that from 26 previous studies (most of them published since 2009) and found that of 4,172 patients receiving an injectable flu vaccine containing traces of egg protein, which included 513 with a history of a severe egg allergy, no cases of anaphylaxis were reported."

National Network for Immunization Information

Seasonal Influenza: Flu Basics - CDC

CDC Says “Take 3” Actions To Fight The Flu

Cochrane re-arranged: support for policies to vaccinate elderly people against influenza Beyer et al. in Vaccine. 2013 Dec 5.