VACCINE RESOURCE COMMITTEE
of the Edmonton Zone Medical Staff Association
View Full List of Vaccine Questions Here
COVID-19 Vaccine Question #9:
Why do people still get COVID after the vaccine?
The virus's coat has changed over time, making the immune response people made to the vaccine AND to previous infections a bit less effective at blocking the virus. There are also mutations to the virus meaning the current vaccine may not apply to new strains of COVID-19. This is why the vaccine has been updated, and may be updated again. There are still many undiagnosed and not severe infections. Since 2022 public health has instead tracked how effective the vaccine is in preventing severe disease and hospitalization.
Fully vaccinated people (including people who had had all updated vaccines) can get COVID-19 infection. In fact most people - vaccinated and unvaccinated- have had COVID more than once. The COVID-19 vaccines are still doing the important job of reducing risk of severe illness and hospitalization.The highly transmissible variants of SARS-CoV-2 have been shown to spread in spite of vaccinations and prior infections but are associated with a greatly reduced risk of severe disease. These strains are also assocated with a lesser risk of Long COVID, especially in vaccinated people.
The fact remains that getting vaccinated is effective in preventing people from getting severely ill or dying from the disease. The vaccines were incredibly effective when initially introduced compared to many of our standard vaccines. Initial trials from both mRNA vaccines have effectiveness around 94% and 95% and slightly lower in the Johnson & Johnson vaccine. However, the pattern now with changes in the strain of virus is more like other vaccine preventable diseases like influenza, where vaccination is imperfect at preventing infection but worth it to prevent severe disease.
Some confusion may have started because people often got vaccinated as COVID-19 was surging, and therefore were at high risk of infection right when they were vaccinated. However, it takes time (officially 2 weeks) after a vaccine to make a full immune response, so cases that happened right around vaccination in surges are not breakthrough infections.
People who are vaccinated have an immune response (antibody and cell mediated) so the most post vaccine cases are non severe nuisance infections, and up to 25% to 30% of the patients who have had breakthrough infections in studies were completely asymptomatic. Fifty to 60% of the patients had some symptoms, which didn’t require medical support. The CDC estimated that 10% of the patients would still require hospitalization, espcially if they were older or had medical issues putting them at higher risk. One to 2% of those hospitalized from breakthrough infections may still die. These numbers may shift because of changes in how well infection rates are detected, and the proportions of people who get significantly ill would be expected to go up when they have less immunity to the current strain.
The virus is continuing to change and may become better at escaping antibodies people have to prior strains. Vaccines will be always be behind the curve now and we cannot predict what the virus will do next, or how often people will need updated vaccines.
Some people have consistently been at higher risk. Patients with immunosuppressed status after organ transplantation, those who are have had blood cancers like lekemia and lymphoma, are on strong immunosuppressive medications, or have conditions that affect immunity like liver disease, cirrhosis and kidney failure still have high risk of severe COVID. People who are older (especially >70) do not have as as strong a vaccine response and have higher chances of getting severe COVID-19 despite being fully vaccinated. These groups are still recommended to get all vaccine updates as directed.
The challenge with this virus, since the beginning of the pandemic in 2020, is that it is evolving, and has been successful in continuing to spread, although thankfully the current risk of severe infection is much lower than it was in the early pandemic. .
Source:
American Medical Association-What doctors wish patients knew about breakthrough COVID infections