COVID-19: Efficacy, Effectiveness, and Side Effects of Vaccines

by Sean Elliott, MD

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    1:00:08 So, that would suggest that the vaccine efficacy was excellent.

    1:00:12 What is vaccine efficacy? It is, the degree to which a vaccine prevents disease and potentially also transmission, so, preventing infectivity is important, under ideal or controlled circumstances.

    1:00:25 Typically, one creates an estimate of the efficacy of any intervention, whether it's in this case a vaccine or medication or something similar, by comparing that that test group, the vaccinated group, with a placebo group, so, efficacy is how well it prevents disease and potentially transmission disease.

    1:00:46 That's what's predicted in a laboratory-controlled setting or a can a clinical study in which everything is controlled.

    1:00:53 What about real world or population level data? This is what is known as the effectiveness estimate.

    1:00:59 This is how well in this case the vaccine actually performs in the real world.

    1:01:03 As you would imagine, that the real world numbers are going to be lower than the carefully controlled efficacy numbers.

    1:01:11 But that's okay, as long as the effectiveness is adequate.

    1:01:14 What one is really looking for of course, is, how effective is the intervention the vaccine against infection? does it do its job in the real world setting and this is the number the effectiveness against infection, that the FDA signed, an a hoped for value of 50%.

    1:01:34 As it turns out that that target was exceeded significantly, by most vaccine products currently available, in the United States and Europe and even parts of India and Africa.

    1:01:48 So, most vaccines are up to 90% effective against symptomatic infection, so, that is fantastic.

    1:01:56 And of course, on a personal level one wants a product a vaccine which will protect one from infection period.

    1:02:03 However, in terms of major use of resources, the absolute morbidity, the challenge that all countries have faced, in the COVID-19 pandemic, has been the burden on health care infrastructure, so, what one really wants to prevent that challenge, is, effectiveness against severe disease.

    1:02:23 How well does the vaccine do against a disease, which requires, the patient to be hospitalized and to consume health care resources and of course, this is the most important factor, not just to prevent death, which is ideal, but also prevent use of the healthcare system.

    1:02:41 And again, major vaccines, certainly the messenger RNA vaccines and several of the adenovirus vector vaccines, are near or at 100% effectiveness against severe disease, that's fantastic.

    1:02:55 Okay, let's fast forward into the real world, one more step and that is knowing that as we attempt to control, the SARS-Coronavirus II in nature, nature abhors a vacuum and new variants, mutations are occurring all the time.

    1:03:11 How well do the vaccines do, in effectiveness against the new virus variants? Most of the vaccines do better against severe disease, even against the variants, but all of them have at least some protection, even as low as 50% against the new variants of concern.

    1:03:28 As we speak, however, surveillance on goes all across the world and new vaccines are still in development, so, any slide regarding this is likely going to be dated, by the time you're watching it.

    1:03:40 Now, vaccines are fantastic, but they are also an intervention, a medical science intervention and so there will be side effects, most of which are minor.

    1:03:50 So, the minor side effects identified with the vaccines noted so far, are, a flu-like illness, soreness at the injection site of course, which, will last a couple days to a week and accompanied sometimes by malaise, low-grade fevers, some sore muscles and that basically reflects a very excellent immune response, by the vaccine recipients.

    1:04:13 Thankfully, major side effects and certainly fatal side effects have been incredibly rare, that's a wonderful thing and that of course then drives the question, was that incredibly rare, “I hadn't seen it before side effect,” in my single vaccine recipient, due to the vaccine, or was it something related to health issues, pre-existing in the vaccine recipient and in many cases it's very difficult to tell, as proof of causality is difficult to achieve.

    1:04:44 So, as an example there have been evidence episodes of myocarditis, in vaccine recipients of one of the messenger RNA vaccines, in vaccine recipients of one of the messenger RNA vaccines, Pfizer or Moderna, mostly young men and those incidence, numbers of myocarditis, in those individuals have exceeded the rate normally witnessed, in a non-vaccine, non-covid pandemic time.

    1:05:10 So, that would suggest that there is some association, why we don't know, but some association, with messenger RNA vaccination and myocarditis, in certain individuals.

    1:05:22 So, what are the side effects that we've witnessed, anaphylaxis, of course, would be a severe side effect, anaphylaxis is possible with any vaccine.

    1:05:32 Fortunately, for the messenger RNA vaccines, in which some episodes have been reported, this is an incredibly low incident, so just 3 to 5 per million vaccine recipients, mostly in women who had pre-existing severe environmental allergies or allergies to food or other products.

    1:05:51 The incidence of thrombosis and thrombocytopenia and specifically, a vaccine-induced immune thrombocytopenia, has been demonstrated in patients who received one of the adenovirus vectored vaccines mostly AstraZeneca and Johnson and Johnson.

    1:06:09 These individuals, have had some significant effects of this thrombosis, including cerebral venous thrombosis and splanchnic vein thrombosis, are the two most common, thrombotic illnesses witnessed in these individuals.

    1:06:26 With the AstraZeneca vaccine, out of 34 million doses administered, you can see the numbers there, just 169 episodes of cerebral venous thrombosis and 53 episodes of splanchnic vein thrombosis, have been demonstrated and confirmed with 18 deaths and based on that, although it is an incredibly rare risk, but the risk is felt to be real.

    1:06:48 So, in many countries, AstraZeneca, is not given to vaccine recipients, who are under age 60, because these cerebral venous and splanchnic venous thrombotic events, all occurred in young adults.

    1:07:02 In the Johnson and Johnson vaccine, out of 20 million doses administered, 25 cases and 9 deaths respectively, with vaccine associated thrombotic thrombocytopenia.

    1:07:13 So, if we then try and compare the risk of vaccine effects, whether they're minor or major or severe or fatal, to other adverse effects, these are great these are great talking points, if one is having this conversation with one's patients, the lifetime chance of dying in a motor vehicle accident, 1 in 103 that's huge.

    1:07:35 The lifetime chance of getting struck by lightning 1 in 15,300 and 10% of those die.

    1:07:40 So, one is absolutely going to be encountering a lot of vaccine hesitancy, due to the side effects, but the risks of death from COVID-19 itself, are far greater, than any theoretical risk from vaccine and one can also use these lifetime risks as well.

    About the Lecture

    The lecture COVID-19: Efficacy, Effectiveness, and Side Effects of Vaccines by Sean Elliott, MD is from the course Coronavirus.

    Included Quiz Questions

    1. Effectiveness against severe disease
    2. Efficacy
    3. Effectiveness
    4. Effectiveness against infection
    5. Effectiveness against new variants
    1. Approximately 4 per million recipients
    2. Approximately 2 per million recipients
    3. Approximately 5 per 100,000 recipients
    4. Approximately 1 per million recipients
    5. Approximately 1 per 100,000 recipients
    1. Viral vector vaccine
    2. Messenger RNA (mRNA) vaccine
    3. Synthetic nanoparticle vaccine
    4. Live-attenuated vaccine
    5. Conjugate vaccine

    Author of lecture COVID-19: Efficacy, Effectiveness, and Side Effects of Vaccines

     Sean Elliott, MD

    Sean Elliott, MD

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