An Israeli study followed 596,618 people who were newly vaccinated with the Pfizer-BioNTech mRNA vaccine during a six-week period from December 20, 2020, to February 1, 2021, and a matched group of the same number of unvaccinated controls (N Engl J Med, April 15, 2021;384:1412-1423). The researchers found that the vaccine offered a high degree of protection, similar to the results shown in the clinical trials. Of 41 deaths from COVID-19 during the follow-up period, 32 occurred in the unvaccinated group and nine in the vaccinated group. Among the documented cases of COVID-19, there were more than three times as many severe cases in the unvaccinated group as in the vaccinated group (174 vs 55).

Of the 4460 documented cases of COVID-19 in the vaccinated group:
• 96% had no symptoms
• 93% of obese subjects had no symptoms
• 92% of people over 70 years of age had no symptoms
• 88% of those who had three or more existing conditions or illnesses had no symptoms
• 86% of those with diabetes had no symptoms
• 84% of immuno-suppressed individuals had no symptoms
• 80% of those with heart disease had no symptoms
• 80% of those with chronic kidney disease had no symptoms
These numbers show that even with the significant protection offered by the vaccine, people with co-existing conditions and the elderly are still at higher risk for complications of COVID-19 than the general population.

Monoclonal Antibodies for Early Treatment
The vast majority of people infected with COVID-19 virus will recover with no treatment whatever. However, certain conditions (listed below) put a person at high risk for serious disease and possibly even death. The U.S. Food and Drug Administration (FDA) issued an Emergency Use Authorization to permit the use of monoclonal antibodies (casirivimab, imdevimab, etesevimab) to treat people at high risk for serious complications of COVID-19. When you are infected or receive a vaccination against COVID-19, you produce protein antibodies that can attach to and kill the virus. Monoclonal antibodies are laboratory-made proteins that are similar to the antibodies that you produce to rid yourself of the virus. The FDA limits the use of monoclonal antibodies to adults over 12 years of age, weighing more than 100 pounds, with positive results of direct SARS-CoV-2 viral testing and with mild to moderate symptoms. People who are at significant risk for severe disease and could benefit from receiving monoclonal antibodies early in the course of COVID-19 include those who:
• are obese (body mass index (BMI) over 34)
• are diabetic
• have chronic kidney disease
• have any immuno-suppressive disease
• are currently receiving immuno-suppressive treatment
• are over 65 years of age or
• are over 55 years of age and have heart or blood vessel disease, high blood pressure, chronic obstructive pulmonary disease or other chronic respiratory disease.
The FDA notes that monoclonal antibodies may worsen symptoms in patients who are hospitalized due to COVID-19 or who require oxygen therapy.

Obesity Increases Risk for Severe COVID-19
A study of 150,000 US adults diagnosed with COVID-19 from March to December 2020 showed that half of the patients were obese and about 28 percent were overweight, based on their body mass index or BMI (JAMA, 2021;325(16):1603).
The COVID-19 patients who were significantly overweight (BMI between 30 and 34.9) had:
• 7% increased risk of hospitalization
• 35% increased risk of mechanical ventilation
• 8% increased risk of dying
The COVID-19 patients who were obese (BMIs greater than 45) had:
• 33% increased risk of hospitalization
• twice average mechanical ventilation rate
• 61% increased risk of death

Most Cases of COVID-19 are Acquired by Breathing Indoor Air
A study from the Massachusetts Institute of Technology found that the risk of suffering COVID-19 indoors is as great at 60 feet as it is at six feet (PNAS, April 27, 2021;118(17)). They report that the amount of time spent in an enclosed area is more important than how far you are from an infected person. The MIT mathematicians calculated indoor risk of COVID-19 based on:
• time spent inside,
• air filtration,
• air circulation,
• immunizations,
• different viral strains,
• use of masks, and
• viral spread by breathing, eating, speaking, singing or other activities.

They found that COVID-19 is far more likely to be spread by breathing infected indoor air than by touching infected objects. Outdoors, the virus is rapidly dispersed after a person talks, breathes, coughs or sneezes, so infection is unlikely and your exposure may depend on how close a person is to you when he spews virus into the air. Indoors, the concentration of virus in the air continuously increases when infected people repeatedly breathe, so you can become infected with COVID-19 by people who are 60 feet or more away from you.
• How long you stay indoors is far more important than how far you are from an infected person because the longer people are there, the more virus remains in the air.
• An infected person breathes out heated viral droplets into warm indoor air that causes the droplets to rise and stay up in the air for a long time. Outdoors the air circulation is better and droplets are likely to fall to the ground far more quickly.
• Masks worn by both infected and susceptible persons can reduce the risk of transmission.

The authors of the study conclude that “to minimize risk of infection, one should avoid spending extended periods in highly populated areas. One is safer in rooms with large volume and high ventilation rates. One is at greater risk in rooms where people are exerting themselves in such a way as to increase their respiration rate and pathogen output, for example, by exercising, singing, or shouting.”

Vaccines Offer the Best Protection
The mathematical model from MIT did not focus on vaccines, but its conclusions about transmission of the virus should encourage people to have all members of their household vaccinated as soon as possible. It is still remotely possible to become infected after being vaccinated, and to infect other people even if you have no symptoms, but a report from the U.S. Centers for Disease Control and Prevention (CDC) on April 26, 2021 shows only about 9000 breakthrough cases of COVID-19 after vaccination, out of 100 million people fully vaccinated, or 0.009 percent.