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Is SARS-CoV-2 Contagious?

Updated October 07, 2023


Yes, SARS-CoV-2, which causes COVID-19, is contagious and is transmitted through aerosolized particles and respiratory droplets. These particles and droplets can be inhaled or can enter the mouth, nose, or eyes. 

The U.S. Centers for Disease Control (CDC) has also stated that SARS-CoV-2 transmission can occur when a person touches a contaminated object and then touches their mouth, nose, or eyes.  The risk of transmission from surfaces is considered to be low, and estimated to occur at a rate of one case per 10,000. 

There is also evidence that the virus can be spread through the fecal-oral route, which supports the recommendation for frequent handwashing. Infected feces can contaminate food, surfaces, and hands, and has the potential to cause illness. 

A study published November 19, 2020 in The Lancet Microbe found that the SARS-CoV-2 virus was most contagious in the first five days after the onset of symptoms. This study also reported that there was no difference in the viral loads among asymptomatic or symptomatic SARS-CoV-2-positive individuals, and research indicated that people without symptoms clear the virus more quickly and are therefore less contagious.  Research studies have also found that viral loads among vaccinated and unvaccinated SARS-CoV-2 positive people to be similar.   

A study conducted in the UK found that the SARS-CoV-2 virus lost 90 percent of its virulence within 20 minutes of being exhaled. After only 10 minutes, the virus lost 50 percent of its ability to infect. Humidity of the environment was also determined to play a role in the ability of the virus to infect. When the environment had a humidity level of less than 50 percent, the virus lost its ability to infect within 10 seconds.   

Natural Immunity after SARS-CoV-2 infection

In January 2021, researchers reported that more than 95 percent of people who recovered from SARS-CoV-2 infection had durable immunity to the virus for at least eight months.  Another study conducted by researchers at the Washington University School of Medicine in St. Louis found that persons who recover from COVID-19 illness, including those with asymptomatic and mild cases, continued to have lasting immunity upon recovery. Study researchers also speculated that immunity following COVID-19 infection would likely endure long-term. 

A study conducted by the Cleveland Clinic Health System in June 2021 involving 52,238 employees found that "Not one of the 1,359 previously infected subjects who remained unvaccinated had a [Covid-19] infection over the duration of the study and vaccination did not reduce the risk. Study authors concluded that persons previously infected with SARS-CoV-2 were unlikely to benefit from COVID-19 vaccination.  Another study specific to health care workers in an urban Massachusetts setting between December of 2020 and September of 2021, when the Delta variant was most prominent, also reported no cases of re-infection with SARS-CoV-2 among those previously infected. 

An August 25, 2021 retrospective study of Israel’s second largest HMO, yet to undergo peer review, compared 673,676 vaccinated individuals who had not been previously infected by SARS-CoV-2, 62,883 unvaccinated individuals and 42,099 previously infected individuals with a single vaccine dose. The study found that natural immunity “confers longer lasting and stronger protection against infection, symptomatic disease, and hospitalization caused by the Delta variant.” 

According to a CDC report published in January 2022 on cases and hospitalizations by COVID-19 vaccination status conducted in New York and California between May 2021 and November 2021, unvaccinated individuals with a history of natural SARS-CoV-2 infection had infection rates of between 14.7 and 29 times lower than unvaccinated individuals without prior infection. In contrast, COVID-19-vaccinated individuals with a past history of SARS-CoV-2 infection were noted to have infection rates that were only between 4.5 and 6.2 times lower. Additionally, hospitalization rates among persons with natural immunity were reported to be between 2 and 6 times lower than those who were vaccinated and had no prior infection. 

Over one hundred studies have reported natural immunity to be equal or better than vaccine acquired immunity.   

According to the CDC, as of early October 2021, there have been approximately 146.6 million COVID-19 infections in the U.S.  A survey of blood donor samples completed in December 2021 and updated in February 2022 found that nearly 95 percent of the U.S. population over age 16 have antibodies to COVID-19, either through infection or vaccination.  In April 2022, health officials estimated that approximately 75 percent of U.S. infants and children from birth to 11 years of age had previously been infected. 

The CDC has acknowledged that they have no evidence that any person with natural immunity due to past infection has been able to transmit the virus to another individual. 

IMPORTANT NOTE: NVIC encourages you to become fully informed about covid-19 and the covid-19 vaccine by reading all sections in the Table of Contents, which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.

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