## Core Concept
SARS (Severe Acute Respiratory Syndrome) is a respiratory illness caused by a coronavirus, specifically known as SARS-CoV. It is characterized by its severe impact on the respiratory system, leading to atypical pneumonia. Understanding the nature of SARS, its transmission, and the availability of vaccines is crucial for managing and preventing outbreaks.

## Why the Correct Answer is Right
The correct statements about SARS are:
- **a) Severe acute respiratory syndrome**: This is the definition of SARS, making it a true statement.
- **b) Documented respiratory route spread**: SARS is known to spread through respiratory droplets, making this statement true.
- **d) Cause atypical pneumonia**: SARS causes a form of atypical pneumonia, which is a key characteristic of the disease.
- **e) Group coronavirus**: SARS is caused by a coronavirus, specifically classified within the group of coronaviruses.

## Why Each Wrong Option is Incorrect
- **Option C: Effective vaccine available**. As of the last update, there is no widely available, effective vaccine for SARS that has been approved for public use, making this statement incorrect.

## Clinical Pearl / High-Yield Fact
A key point to remember is that SARS is a highly contagious and sometimes fatal respiratory illness. The outbreak in 2003 highlighted the importance of rapid identification and isolation of cases, as well as strict infection control measures to prevent spread. The lack of an effective vaccine and the potential for future outbreaks make SARS a significant public health concern.

## Correct Answer: D.