SARS-CoV-2 and the COVID-19 Vaccine

A novel coronavirus (SARS-CoV-2) that emerged from Wuhan, China in 2019 is currently causing worldwide panic, with many governments resorting to mandatory quarantines and travel restrictions. Most of what we know about COVID-19, the disease caused by SARS-CoV-2, has been derived from general scientific knowledge about related coronaviruses and from clinical publications and data derived from the diseases epicenter in Wuhan.

Covid-19 spreads very quickly because infected individuals typically do not show symptoms for 5-7 days post-infection. In most individuals, particularly under the age of 30, the symptoms are extremely mild, more resembling a cold or flu, and often go unnoticed and likely unreported. The more severe cases, which can lead to fatality, occur in patients that are over 65 years of age, or over 40 years of age with one or more comorbidities. In particular, individuals with underlying hypertension, heart disease, respiratory disease, or diabetes are at a much higher risk of developing severe symptoms. In addition, males are nearly twice as likely to develop more severe symptoms than are women, for reasons that are still not understood.

Early in 2021, several vaccines against SARS-CoV-2 were made available by Pfizer/BioNTech, Moderna, and Janssen (Johnson & Johnson). The highest risk individuals (>70 years of age and residents of long-term care facilities), as well as many front-line health care workers, were offered the first round of vaccinations. After a period of time, vaccines were made available to other age groups, until all individuals over 16 years of age were eligible for free vaccination by mid-summer. There are, however, many individuals and groups of individuals who are refusing these vaccines due to strongly-held political/religious beliefs and/or misinformation that is being spread through social media.

How do vaccines work? And how do the two-shot Moderna and Pfizer vaccines differ from the one-shot Janssen vaccine? How does this vaccination protect the individual from coming down with COVID-19? How common are so-called breakthrough infections, and what causes them? Are they a cause for concern?

This is for pathophysiology