On February 26, 2015, the United States Centers for Disease Control and Prevention (CDC) updated its vaccine effectiveness estimates for the vaccine against the influenza A and B H3N2 viruses for the 2014-2015 season. The CDC announced that the vaccine was 18% effective against the predominant A strain of the flu and 45% effective against the B strain.1 An earlier CDC estimate (on January 16) of the vaccine’s effectiveness against the A strain was 23%.1
However, even with such low effectiveness rates, the CDC recommended that people get the vaccine based on the logic that a low degree of effectiveness is still “better than nothing.” According to the CDC, even a vaccine effectiveness of only 10% in a “severe” season could prevent about 13,000 hospitalizations.2
Even as they acknowledge the shortcomings of this year’s vaccine, public health officials have insisted that those who get vaccinated are still better off.3
In January, when the CDC’s effectiveness estimate for the the 2014-2015 influenza vaccine was at 23%, Dr. Marc Siegel, a professor of medicine at New York University’s Langone Medical Center, was quoted as saying, “Twenty-three percent is better than nothing, and there is no downside to getting the vaccine.”4
But what exactly does the CDC mean by “vaccine effectiveness”? Essentially, what the CDC is talking about is a vaccine’s “ability to prevent” an illness or a disease.5 More specifically:
Effectiveness represents the percentage reduction in the frequency of influenza infections among people vaccinated compared with the frequency among those who were not vaccinated, assuming that the vaccine is the cause of this reduction.6
When the CDC gives a certain percentage for influenza vaccine effectiveness, such as the 18% figure, the estimate “represents the reduction in risk provided by the flu vaccine.” According to the CDC, its vaccine effectiveness studies “commonly measure laboratory confirmed flu illness that results in a doctor’s visit or urgent care visit as an outcome.” Thus, a vaccine effectiveness estimate of 18% means 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 18%.5
Note here the words “flu illness.” In its “guesstimates” for the number of people who have come down with influenza in past years, the CDC has taken the liberty of including those hospitalized “not just with influenza but also with pneumonia, respiratory and circulatory illnesses—which they counted as probably associated with influenza.”6 CDC officials have taken the same liberty when estimating the number of people who have died of influenza. They do not only count those who had lab confirmed type A or type B influenza, they also throw in “other respiratory, circulatory, cardiac and pulmonary deaths they thought might have been associated with influenza“6—when the death could have been related to other types of viruses and bacteria causing symptoms resembling influenza.
This obviously tends to distort the picture from the outset. The truth is nobody knows exactly how many people in the U.S. die from influenza and how many die from flu-like respiratory illnesses that look like influenza but are caused by other types of viruses or bacteria.
There are two types of clinical studies used by vaccine manufacturers and the CDC to evaluate the effectiveness of a vaccine, such as the influenza vaccine. The first type is referred to as a randomized control trial (RCT) and, ideally, a well designed clinical trial to evaluate the effectiveness (or safety) of a vaccine is a comparison of a group of individuals who receive the vaccine and a group of individuals who do not receive the vaccine.
In a RCT, volunteers are assigned randomly to either a group that receives vaccine or a group that receives a placebo (e.g., a shot of saline), and vaccine efficacy is measured by comparing the frequency of influenza illness in the vaccinated and the unvaccinated groups. RCTs are required before a new vaccine is licensed for routine use by a national regulatory authority, such as the Food and Drug Administration (FDA) in the United States.7
The second type is an observational study.
In observational studies the study participants make their own decisions about whether or not to be vaccinated. In this type of study, vaccine effectiveness is measured by comparing the frequency of influenza illness in the vaccinated and unvaccinated groups, usually with adjustment for factors (like presence of chronic medical conditions) that may vary between the groups.
Interestingly, there is a difference between the way CDC and medical doctors measure the effectiveness of vaccines, and the way vaccine researchers and manufacturers measure vaccine effectiveness or “efficacy.” While vaccine effectiveness is a look at the perceived clinical “real world” impact of vaccines on preventing illness and disease, vaccine efficacy is a lab measurement of vaccines being able to stimulate the production of antibodies in a research setting.8
So when a vaccine researcher states that the efficacy of a vaccine is at least 95%, as is supposedly the case with Merck’s MMR (mumps, measles, rubella) vaccine, he or she is referring to the vaccine’s ability to stimulate antibodies. That is not the same as the vaccine being at least 95% successful in protecting you from contracting the diseases. The underlying theory of vaccine effectiveness is based on the assumption that a certain level, or titer, of antibodies in your blood against a certain disease will make you immune to that disease. That assumption has repeatedly been proven to be false in many cases.
There continue to be numerous outbreaks of infectious diseases, in which fully vaccinated people with high antibody titers become infected. In the case of pertussis (whooping cough), for example, the CDC has stated: “The findings of efficacy studies have not demonstrated a direct correlation between antibody responses and protection against pertussis disease.”9
In the case of varicella zoster (chickenpox), according to the CDC, “No data exist regarding post exposure efficacy of the current varicella virus vaccine.”10 Even the manufacturer of the chickenpox vaccine Varivax, Merck, admits as much.
Varivax induces both cell-mediated and humoral immune responses to varicella-zoster virus. The relative contributions of humoral immunity and cell-mediated immunity to protection from varicella are unknown.11
In the case of Haemophilus influenza type B, the HibTiter vaccine’s “contribution to clinical protection is unknown.”12
In short, we do not know how effective vaccines are because there are big vaccine science knowledge gaps. While it is possible to gauge the research efficacy of vaccines based on their success in stimulating antibody production, estimating their actual clinical effectiveness seems to be more of a guessing game than anything else. Again, the reason is that the presence of antibodies does not necessarily mean you are protected.
This is the white elephant in the room that public health officials and the pharmaceutical industry do not wish to acknowledge, because it throws a monkey wrench into the flawed logic they use to aggressively push for one-size-fits-all “no exceptions” vaccine policies and laws.
Note: For the Spanish translation of this article, see “Sobre la cuestión de la eficacia de las vacunas” in Argentina sin Vacunas.
1 Centers for Disease Control and Prevention. CDC Presents Updated Estimates of Flu Vaccine Effectiveness for the 2014-2015 Season. CDC.gov (press release) Feb. 26, 2015.
2 Centers for Disease Control and Prevention. News and Media Resources. Immunization Works Newsletter January 2015.
3 Dennis B. CDC: Flu vaccine only 23 percent effective this season, but still better than nothing. The Washington Post Jan. 15, 2015.
4 Reinberg S. This Year’s Flu Shot Is Only 23% Effective. HealthDay Jan. 16, 2015.
5 Centers for Disease Control and Prevention. Vaccine Effectiveness – How Well Does the Flu Vaccine Work?. CDC.gov.
6 Fisher BL. Influenza Deaths: The Hype vs. The Evidence. NVIC.org Oct. 3, 2012.
7 Centers for Disease Control and Prevention. Flu Vaccine Effectiveness: Questions and Answers for Health Professionals. CDC.gov.
8 Tenpenny S. Vaccine Assumptions – Are They Effective?. Ezinearticles.com May 19, 2007.
9 Centers for Disease Control and Prevention. Pertussis Vaccination: Use of Acellular Pertussis Vaccines Among Infants and Young Children. Morbidity and Mortality Weekly Report May 28, 1997; 46(RR-7): p 4.
10 Centers for Disease Control and Prevention. Prevention of Varicella. Morbidity and Mortality Weekly Report July 12, 1996; 45(RR-11): p 10.
11 Merck. Varivax: Highlights of Prescribing Information. Merck.com p 7.
12 RxList. HiTiter. RxList.com.