Long-Term Immunity for COVID-19

After more than two years living in a pandemic, we all have heard about the role of antibodies* to grant us immunity. If you want to read more about this topic, check out our post and video. In general, antibodies protect us from getting the same infection for some period, but how long this protection lasts differs for each person and disease (read here for more information). 

Recent research measured the efficiency of antibodies to fight the Omicron variant and realized a booster dose helped significantly in this case [1]. There are two hypotheses for how this happens:

1. Perhaps it increases the interaction between antibodies and spike protein, even if the spike protein has new mutations.

2. It could boost the antibodies so even low-level antibodies that target non-mutated regions of the spike become amplified.

There are currently several commercial tests to check the number of antibodies your body has produced called antibody or serology tests [2], and lots of people are taking these tests in hopes of getting a big number of antibodies. However, there are several reasons why the CDC and the FDA are not recommending them [3,4]:

1. At the beginning of an active COVID-19 infection the number of antibodies is very low, because it takes 1-3 weeks for the body to start making them. If you have symptoms of COVID-19, you should get a PCR or an antigen test to detect the current infection. More information on these topics on “How do COVID-19 PCR tests work?” and “How do COVID-19 rapid tests work?”.

2. If you get an antibody test after receiving the vaccine, you may test positive for some (not all) antibodies. This depends on the type of antibody the specific test detects.

3. There are also cases of false positives (the test is positive even though you don’t have antibodies) and false negatives (the test is negative even though you have antibodies) associated with each test.

The main idea for these tests is to know if you have or not antibodies, and not the specific amount. Making antibodies consume a lot of energy the body could use for other activities [5]. To avoid spending time, energy, and means, B-cells stop the production of antibodies once the threat has passed and the body is out of danger, reducing their number. 

The idea that antibodies decay over time is worrisome, but it doesn’t mean you will be unprotected against COVID-19 in the future. In fact, the organism has other means to continue granting us immunity* over time, called mediated immunity [6]. This type of immunity is done by two types of lymphocytes or T-cells: cytotoxic T-cells and helper T-cells. Cytotoxic T-cells are in charge of eliminating infected cells so the pathogen cannot continue multiplying and damaging our body. On the other hand, Helper T-cells, recognize foreign antigens and potentiate antibody production and activation of Cytotoxic T-cells. Even though they do not eliminate the pathogen directly, their role is crucial to maximize the immune response.

Furthermore, research has proved that T-cells can also help us fight the Omicron variant by killing infected cells. Indeed, lymphocytes are better equipped to fight variants because they do not only focus on the spike protein [7].

Therefore, the absence of antibodies does not imply a lack of immunity. Cell-mediated immunity (T-lymphocytes) can protect us from the virus even though the number of antibodies has decreased. There are cellular tests that detect the response mediated by T-lymphocytes, providing much more information about our immunity. The problem is that they are very complex and expensive, so they are mostly only used for research purposes. However, in general, it is not necessary to get any test since cell-mediated immunity is generated in the vast majority of people. Trust your body, it has evolved over millions of years to protect you and it will continue to do so. 

*Antibody - A molecule produced by immune cells that recognizes and binds to another molecule that is foreign to the organism, the antigen. By binding to the antigen, the antibody can tag the foreign molecule for destruction or directly neutralizes it.

**Immunity - An established memory and quick response that our bodies have against infection by pathogens or foreign molecules that enter our bodies. When we combat and survive an infection, we normally develop resistance against the organism or molecule that caused the infection. Vaccines train our bodies to develop immunity against pathogens, without the need to be infected by them first.

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Written by: Nicole

Edited by: María and Natasha

BioDecoded is a volunteer group committed to sharing accurate scientific information. For more information about vaccines and their safety profile, please see previous posts or consult with your personal physician. If you have any questions about this topic, please comment or send them to our email.

References:

1.  Garcia-Beltran, et al., 2022. mRNA-based COVID-19 vaccine boosters induce neutralizing immunity against SARS-CoV-2 Omicron variant. Cell, 185(3), pp.457-466.e4. Available at: https://www.cell.com/action/showPdf?pii=S0092-8674%2821%2901496-3

2. Antibody Serology Tests: MedlinePlus Medical Test, Medlineplus.gov (2021). Available at: https://medlineplus.gov/lab-tests/antibody-serology-tests/(Accessed: 25 April 2022).

3. Test for past infection, CDC (2021). Available at: https://www.cdc.gov/coronavirus/2019-ncov/testing/serology-overview.html(Accessed: 25 April 2022).

4. Antibody Testing Not Recommended to Assess Immunity After Vaccination (2022). Available at: https://www.fda.gov/medical-devices/safety-communications/antibody-testing-not-currently-recommended-assess-immunity-after-covid-19-vaccination-fda-safety(Accessed: 25 April 2022).

5. Segerstrom, S. (2007). Stress, Energy, and Immunity, Current Directions in Psychological Science, 16(6), pp. 326-330. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2475648/

6. Institute, T. et al. (2022) ‘Killer’ immune cells still recognize Omicron variant, Nature.com. Available at: https://www.nature.com/articles/d41586-022-00063-0#:~:text=They%20have%20found%20that%20the,respond%20to%20Omicron2%E2%80%934(Accessed: 25 April 2022).