Take Care of Your Immunity Even if You’re Vaccinated

COVID-19 vaccination adherence has been increasing dramatically. But some people are still confused about what that means for their immunity, and if they can still contract the virus. This article collects information provided from various leading health authorities to shed light on COVID-19 breakthrough infections and immunity.

How Do COVID-19 Vaccines Work?1

All COVID-19 vaccines work to create a natural immune response to an element of the COVID-19 virus. This means that if we come in contact with the COVID-19 virus, our immune cells will recognize it and remember how to fight it off. Vaccines are not able to stop you from coming in contact with the virus.

Although they work in the same way, different vaccines have different methods of delivering the element of the virus, which will be recognized and attacked by the body.

  • mRNA vaccines (Pfizer-BioNTech or Moderna) contain material from the virus that causes COVID-19. This gives our cells the instructions for how to make a harmless protein that is unique to the virus. After our cells make copies of the protein, they destroy the genetic material from the vaccine.
  • Protein subunit vaccines (vaccines under development) contain harmless pieces of proteins from the virus that causes COVID-19.
  • Vector vaccines (Johnson & Johnson’s Janssen) contain a modified version of a different virus than the one that causes COVID-19. Inside the shell of the modified virus, there is material from the virus that causes COVID-19. Once inside our cells, the genetic material gives instructions to make a protein that is unique to the virus that causes COVID-19. Using these instructions, our cells make copies of the protein before destroying the genetic material from the vaccine.

What is a Breakthrough Infection?2

A breakthrough infection is an infection of the pathogen (i.e. a virus) after you have been vaccinated. This is an expected occurrence for a small percentage of those receiving any vaccine, since no vaccine for any disease is 100% effective in preventing infection in every person who receives it.

Breakthrough COVID-19 infections happen when someone who has been fully vaccinated becomes infected. Earlier data approximated COVID-19 breakthrough infections at a rate of about 1 in 5,000. However, more recent data has shown breakthrough infection rates of approximately 1 in 100 fully vaccinated people.

Risk Factors of COVID-19 Breakthrough Infection

Anyone can get a COVID-19 breakthrough infection, however, having a weakened immune system is a leading risk factor.2 Causes of a weakened immune system:

  • Age: our immune system tends to become less robust against external pathogens as we age. This leads to increased risk of infection and a higher case fatality rate for COVID-19.3
  • Certain medical conditions or treatments: these include organ transplants, HIV and some cancers and chemotherapy
  • Smoking: chronic smoking has been shown to compromise respiratory function in adults and may lead to increased susceptibility to COVID-194,5
  • Poor nutrient status: Malnutrition or nutritional deficiencies can result in lowered immunity and reduced resistance to infection6

We all need to work together to keep ourselves and each other healthy. Some measures like vaccines, work at a societal level to reduce infection rates in the population. Other measures like diet and lifestyle, work at an individual level.

聯絡我們 to talk to our team about how to keep your immune system working optimally.

*This article is for educational purposes only. Learn more about COVID-19 in Hong Kong.


  1. Understanding How COVID-19 Vaccines Work. Available at: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/how-they-work.html.
  2. John Hopkins. Breakthrough Infections: Coronavirus After Vaccination. Available at: https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/breakthrough-infections-coronavirus-after-vaccination.
  3. Montecino-Rodriguez, Encarnacion et al. “Causes, consequences, and reversal of immune system aging.” The Journal of clinical investigation. 123,3 (2013): 958-65. doi:10.1172/JCI64096
  4. Burchfiel, CM, et al. Effects of smoking and smoking cessation on longitudinal decline in pulmonary function. 1995. Am J Respir Crit Care Med. 1995 Jun;151(6):1778-85.
  5. Kenfield SA., et al. Burden of smoking on cause-specific mortality: application to the Nurses’ Health Study. Tob Control. 2010 Jun; 19(3): 248–254. doi: 10.1136/tc.2009.032839
  6. Karacabey K., et al. The Effect of Nutritional Elements on the Immune System. J Obes Wt Loss Ther 2:152. doi:10.4172/2165-7904.1000152
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