What are the differences and will they work?
COVID-19 has dominated our lives for the better part of a year and yet we are left with more questions than we are answers. One of these questions most frequently brought up is how long will the antibodies be effective after a vaccination is given?
IgG is a specific type of antibody that the human body keeps on call in case it encounters a future infection by the same pathogen. IgG antibodies stay in the bloodstream long-term, potentially lifelong, to prevent reinfection by
repeat pathogens. However, not every IgG antibody will remain effective forever, and immunity can eventually wan or be lost entirely.(1)
There are currently three vaccine manufacturing candidates in the running to be the first approved COVID-19 vaccine, with Moderna, University of Oxford (AstraZenecaOxford), and Pfizer-BioNTech all developing one of these viable options.(4)
THE MODERNA VACCINE
Moderna’s COVID-19 vaccine uses messenger RNA, or mRNA, which is showing efficacy of over 95% in early clinical trials. The mRNA codes for the spike protein of the virus and uses our cells own protein synthesis apparatus to create multiple copies that our bodies can recognize and form antibodies against (see diagram below). The Pfizer vaccine also uses
mRNA. Moderna is expected to have over 20 million doses available to ship by the end of the 2020 calendar year.(5) Moderna’s claims regarding side effects indicate a lack of serious risk, including fatigue, muscle and joint pain, and headache.(8)
THE ASTRAZENECA VACCINE
Data on the AstraZeneca-Oxford vaccine shows only 62% effectiveness with its two dose regimen, though claims of lower costs hope to offset the lower protection rates.(6) Recent data for this vaccine seem to be lowering its validity in the American market due to risky side effects, including a report of transverse myelitits, an inflammatory disorder of the spinal cord.(9) Oddly enough, an error in the clinical trials led to a serendipitous finding. When only a half dose of the initial injection was mistakenly given, the efficacy shot up to 90%.(12)
THE PFIZER VACCINE
In a recent New York Times article, PfizerBioNTech also claimed its vaccine is 95% effective and shows no serious side effects, only low percentages of fatigue and headache. Pfizer hopes to receive EUA (Emergency Use Authorization) within a matter of days, placing itself as a frontrunner in terms of distribution scheduling.(7) However, Pfizer currently has stringent limitations regarding temperature controls for its vaccine distribution. Its shelf life is only five days in a regular -20 deg C freezer.(8) Long term storage must be carried out in a -70 deg C ultra-low freezer.
Most of what we know in regard to COVID-19 and its relationship with IgG has been determined from other, previous Coronavirus infections. The main conclusions drawn from previous Coronaviridae viral family studies remain cautiously optimistic. However, immediately following infection or
vaccination, antibody concentrations have been found to decrease over time resulting in a greater risk for re-infection, especially in mild cases of infection. This suggests that multiple rounds of vaccine therapy may be necessary to keep Coronavirus IgG antibodies boosted to the level they can prevent a serious infection.(2)(3)
As for how long the vaccines will offer protection; that is not yet known and will take time to make that determination. Another possible reason for vaccine failure would be if the virus mutates in such a way to decrease the efficacy of the vaccine.
The human immune system is a vast and complex set of machinery, and COVID-19 is proving to be quite an opponent. As vaccines begin to become more widely available, it looks hopeful that we will have the tools to win this drawn-out war against an invisible enemy, especially with this competitive race to the vaccination finish line.
Authored by Lo Johnson
References:
(1) 2018 review performed by Mary M. Mary, PhD, DABCC, FACC, Global
Medical and Scientific Affairs, Beckman Coulter, 16-NOV-2020.
(2) Sariol, A, Perlman, S. (2020). Lessons for COVID-19 Immunity from Other
Coronavirus Infections. Elsevier Public Health Emergency Collection, 53(2), 248-263.
(3) Fact Sheet for Healthcare Providers qSARS-CoV-2 IgG/IgM Rapid Test – Cellex Inc.. 16-NOV-2020
(4) Craven, J. (Nov 2020). COVID-19 vaccine tracker. Regulatory Affairs
Professionals Society. Retrieved from https://www.raps.org/news-andarticles/news-articles/2020/3/covid-19- vaccine-tracker
(5) Moderna’s COVID-19 Vaccine Candidate Meets its Primary Efficacy
Endpoint in the First Interim Analysis of the Phase 3 COVE Study [moderna]
(2020). Retreived from https://investors.modernatx.com/node/10316/pdf. 23-NOV-2020.
(6) Gallagher, J. Covid-19: Oxford University vaccine is highly effective.
BBC News. (Nov 2020). Retrieved from https://www.bbc.com/news/health55040635.
(7) Thomas, K. (Nov 2020). New Pfizer Results: Coronavirus Vaccine is Safe
and 95% Effective. The New York Times.
(8) Wadman, M. (Nov 2020). Public needs to prep for vaccine side effects.
Science Mag, 370(6520), 1022.
(9) Allen, A, Szabo, L. (Sep 2020). NIH ‘very concerned’ about serious side
effect in coronavirus vaccine trial. Fierce Pharma. Retrieved from
https://www.fiercepharma.com/vaccines/nih-very-concerned-about-seriousside-effect-coronavirus-vaccine-trial
(10) About the Oxford COVID-19 vaccine. (JUL 2020) University of Oxford. 23-JUL-2020
(11)Cao, S. Covid-19 Vaccine Prices Revealed from Pfizer, Moderna, and
AztraZeneca. Observer. (Nov 2020).
(12) https://www.healthline.com/healthnews/what-to-know-about-theastrazeneca-vaccine-controversy
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