What is the risk of getting COVID-19 for a vaccinated person?
Text updated on 2021-09-07
It is possible to get COVID-19 if you have close contact with a contagious person, because a vaccine never provides 100% protection, but the risk is low. Moreover, if you catch COVID-19 after being vaccinated, there is little chance of getting a severe form of the disease.
A vaccinated person cannot get COVID just with the vaccine, because the vaccine cannot induce the production of infectious virus particles in the vaccinated person. This is because the virus, in order to be infectious, must be made up of several components (its genetic material, specific proteins attached to the genetic material, a lipid membrane, various membrane proteins including the spike protein). However, in the Pfizer, Moderna, Astrazeneca, Janssen and Sputnik vaccines, there is only one element (the spike protein) and this element is not sufficient to trigger the production of infectious virus particles in the vaccine recipient. See the question What are the different types of vaccines against COVID-19 ?.
Vaccination against COVID-19 with the Pfizer, Moderna and Astrazeneca vaccines provides approximately 90% protection against severe forms of the disease and 70-90% protection against mild forms of the disease. This means that even if you are fully vaccinated, it is possible to catch the COVID-19. But the risk is very low. See the question How many days after vaccination does protection against the coronavirus start? What is reassuring is that if you are vaccinated and you catch COVID-19In the vast majority of cases, the symptoms will be mild.
Real-life protection rates against severe forms and hospitalizations :
- Pfizer-BioNTech vaccine: after the second dose : 95% (Alpha variant), 95% (Beta and Gamma variants), 96% (Delta variant) after the first dose : 80% (Alpha variant), 77% (Beta and Gamma variants), 78-94% (Delta variant)
- Moderna vaccine : after the second dose : 94% for the alpha variant after the first dose : 79% for the alpha variant 89% for beta and gamma variants 96% for the delta variant
- Astrazeneca vaccine : after the second dose : 86% for the alpha variant 92% for the delta variant after the first dose : 76-85% for the alpha variant 83% for beta and gamma variants 71-88% for the delta variant
- Jannssen vaccine (1 dose) : 82% for beta and gamma variants
Regularly updated compilation of vaccine effectiveness COVID. Vaccine effectiveness is measured in several ways: (1) prevention of infection, i.e. the effectiveness of the vaccine in stopping transmission of the virus from one person to another. An exposed person will not contract the virus, nor, by definition, develop symptoms or disease; (2) prevention of asymptomatic disease: the vaccine's effectiveness in preventing an exposed person who has contracted the virus from developing symptoms; (3) prevention of symptomatic disease: the vaccine's effectiveness in preventing an exposed individual from suffering symptoms following infection COVID-19(3) prevention of severe disease and death: the effectiveness of the vaccine in preventing an exposed individual from developing severe symptoms that often require hospitalization and lead to death.IHME (2021) COVID-19 vaccine efficacy summary.
This study of 36,659 people working in the health sector showed that after a full vaccination with RNA vaccines (Pfizer or Moderna) the risk of being infected with SARS-CoV-2 is 0.05%.Keehner, J., Horton, L. E., Pfeffer, M. A., Longhurst, C. A., Schooley, R. T., Currier, J. S., ... & Torriani, F. J. (2021). SARS-CoV-2 infection after vaccination in health care workers in California. New England Journal of Medicine, 384(18), 1774-1775.
This study shows that in people who are infected with SARS-CoV-2 after being vaccinated, the viral load is reduced. The reduction in viral load will decrease the shedding of infected particles by SARS-CoV-2 and may therefore affect infectivity.Levine-Tiefenbrun, M., Yelin, I., Katz, R. et al. Initial report of decreased SARS-CoV-2 viral load after inoculation with the BNT162b2 vaccine. Nat Med 27, 790-792 (2021).
This study shows that in patients hospitalised with severe COVID-19viral load is associated with mortality: the lower the viral load, the lower the risk of mortality.Pujadas, E., Chaudhry, F., McBride, R., Richter, F., Zhao, S., Wajnberg, A., ... & Cordon-Cardo, C. (2020). SARS-CoV-2 viral load predicts COVID-19 mortality. medRxiv.
Summary of the efficacy of different vaccines in relation to different variants of the coronavirus SARS-CoV-2.Korsia-Meffre, S. (2021) Variants of SARS-CoV-2 : how effective are real-life vaccines? Vidal.fr.