key: cord-0729870-vrd5bs8z
authors: Shader, Richard I.
title: COVID-19 Vaccine Effectiveness
date: 2021-05-05
journal: Clin Ther
DOI: 10.1016/j.clinthera.2021.04.016
sha: 74ae8fe690129f4a262d06f6e665fd33100a881f
doc_id: 729870
cord_uid: vrd5bs8z

nan

Richard I. Shader, M.D.

I am often asked variants of these questions: "Are the various Covid-19 vaccines really good?" and "Is one better than the others?" My typical response is: "Yes, from reading what has been published they appear to work, and they may be comparable." Notice that I use several qualifying wordsappear and may be. In many reports and briefings, we are told that several vaccines are 94 to 95% effective. For example, in the Baden and colleagues study of the Moderna mRNA-1273 vaccine, the authors concluded that the vaccine "…showed 94.1% efficacy at preventing Covid-19 illness." 1 My first concern is that this and similar statements omit a very important modifying phrase: "…in the population studied." In this same Moderna study, one of the inclusion criteria indicates that volunteers were from "…locations or circumstances that put them at an appreciable risk of SARS-CoV-2 infection, a high risk of severe Covid-19, or both." SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is the virus that causes Covid-19 illness. However, in this and other trials, we do not know if study volunteers were actually in close enough contact with persons who were ill from Covid-19, or whether those exposed were exposed to persons with comparable SARS-CoV-2 viral loads or even the same mutations of this virus.

Why do I raise this issue? Shouldn't the large samples sizes and the use of randomization obviate these concerns? Perhaps, but do they? In 2020, the population of the United States (US) was approximately 330 million persons. 2 are there yet to be discovered identifiable risk factors for vulnerability?

Currently, we do not know how long induced immunity will last, whether periodic booster shots may be required, or whether new mutations will arise which are resistant to currently available vaccines. We also need to find ways to protect immunocompromised patients. To use a baseball analogy, we have gotten on base safely with the currently available vaccines.

However, that is not the same as hitting a home run or winning the game.

Continuing investment is needed to protect us all from these and other viruses that may leap from animals to man. 6

The currently available messenger RNA vaccines for preventing SARs-CoV-2 viral infections appear to be effective, even though some important questions remain unanswered. Strong real world evidence from both health care workers and from a large population study of Israeli patients confirm the benefits of vaccination. [7] [8] [9] Everyone who can safely take these vaccines should do soboth to protect themselves and others. Those who are hesitant or fearful should be helped by professionals and community and religious leaders to overcome their resistance. Only then can we be more sure of being on the path to health and safety.

The author has no potential or real conflicts of interest to disclose with respect to this letter.

Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine

Cases of Covid-19 in the United States

Safety and efficacy of the BNT162b2 mRNA Covid-19 vaccine

False negative rate of COVID-19 PCR testing: a discordant testing analysis

Zoonotic Viruses: The mysterious leap from animals to man

SARS-CoV-2 infection after vaccination in health care workers in California

Early evidence of the effect of SARS-CoV-2 vaccine at one medical center

BNT162b2 mRNA Covid-19 vaccine in a nationwide mass vaccination setting