After over a year of masks, hand-washing, and social distancing, the current rate of vaccination is a relief. So far, Pfizer-BioNTech and Moderna have both shown more than 90% effectiveness during clinical trials [1]. In this text, we discuss in detail how scientists use the functioning of the immune system in vaccines to train our cells to fight infections quickly and efficiently. However, researchers still do not fully understand to what degree viral transmission is possible between vaccinated and non-vaccinated individuals. There are two reasons for this mystery.
Firstly, the clinical trials were not designed to test viral transmission between vaccinated and non-vaccinated individuals. Instead, the trials were designed to determine the safety of the vaccine and the degree to which vaccination prevented exposed individuals from getting sick. Safety and efficacy were the most pressing concerns during those trials.
Secondly, there is a lack of scientific evidence describing the type of antibodies* generated by COVID-19 vaccines. B-cells constitute a large portion of the adaptive immunity and are responsible for documenting past infections that grant immunity. Antibodies are produced by B-cells, they seek out, target, and neutralize invading pathogens**. Following the body’s recovery from infection, or following vaccination, the antibodies continue circulating through the body.
The antibodies produced following vaccination, known as IgG antibodies, grant long term immunity. Dr. Mathew Woodruff, from the Lowance Centre for Human Immunology at Emory University, remarks that IgG antibodies identify and target threats that have already entered the body [2]. Therefore, IgG prevents illnesses, but they cannot prevent transmission. On the contrary, IgA antibodies (a different type of antibody) are required to prevent transmission. This last type of antibodies are localized in mucosal surfaces like the nose, throat, and lungs to prevent viral entry into the body.
Early studies demonstrate that people who have recovered from a COVID-19 infection can produce IgA antibodies, preventing them from getting infected again and spreading the virus to others for 2 to 3 months [3]. On the other hand, recent studies show that following vaccination, IgA antibodies significantly rise following the first and second doses, but their levels are not maintained. Instead, IgA levels decline rapidly in the following days [4]. This suggests that additional work is necessary to guarantee that the IgA levels provided by vaccination can prevent transmission.
As more research becomes available, the health authorities of each country will be able to make informed decisions regarding the wearing of masks for people who are vaccinated. For example, the CDC has already indicated that you can resume your activities without the need of a mask if you are fully vaccinated [5]. However, until this information is available everywhere, it is vital that all vaccinated individuals wear masks, wash their hands, and practice social distancing when around those who haven’t yet received the vaccine – just in case.
This also underlines the importance of getting as many individuals vaccinated as possible. As herd immunity approaches, the virus will have greater difficulty finding non-vaccinated individuals to infect. This will effectively halt the spread of the virus, bringing society one step closer to “normal”.
*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.
**Pathogens - any microorganism that can cause infection and disease.
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Written by: María
Edited by: Adrian and Natasha
BioDecoded is a volunteer group committed to sharing accurate scientific information. We cannot offer any specific health advice. If you have any doubts about getting vaccinated due to previous health conditions, please speak with your healthcare professional or family physician. Your doctor can revise your medical history and advise you on the best path to follow. If you have any questions about this topic, please comment or send them to our email.
References:
National Center for Immunization and Respiratory Diseases (NCIRD), D. of V. D. Different COVID-19 Vaccines | CDC. (2021). Available at: https: www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines.html. (Accessed: 10th May 2021)
Woodruff, M. C. et al. Extrafollicular B cell responses correlate with neutralizing antibodies and morbidity in COVID-19. Nat. Immunol. 21, 1506–1516 (2020). Available at: https://www.nature.com/articles/s41590-020-00814-z
Wang, Z. et al. Enhanced SARS-CoV-2 neutralization by dimeric IgA. Sci. Transl. Med. 13, (2021). Available at: https://pubmed.ncbi.nlm.nih.gov/33288661/
Campillo-Luna, J., Wisnewski, A. V & Redlich, C. A. Human IgG and IgA responses to COVID-19 mRNA vaccines. medRxiv 2021.03.23.21254060 (2021). Available at: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0249499
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