A collection of PNWU scientists weigh in on the benefits of vaccine-induced immunity versus immunity from a previous COVID-19 infection.
Infection-Induced Immunity vs. Vaccine-Induced Immunity
COVID-19 vaccines offer the best form of protection from the severe outcomes of COVID and SARS CoV-2 infection.
Previous COVID-19 infection may provide immune protection, but that immunity is highly variable and unpredictable. Vaccines, however, have been proven to provide enhanced and prolonged protection against COVID-19, including in people previously infected with SARS CoV-2.
COVID-19’s correlate of protection — the exact immunological response required to protect someone against infection and severe disease — has yet to be determined. With that said, achieving any level of immunity via COVID-19 infection is unpredictable and extremely dangerous. COVID-19 infections can result in hospitalization, long-term effects including heart and lung damage, or death. We are still learning more about the long-term effects of COVID-19 because it is such a new disease. Vaccines, however, are proven to protect individuals against the disease.
An Immunity Boost
Studies show that people who have already been infected by SARS-CoV-2 can benefit significantly from vaccination, demonstrating a vaccine-induced immunity boost. When immunity that is generated from infection is combined with vaccine-generated immunity, a larger-than-expected immune response arises.
Upon receiving the first dose of a COVID mRNA vaccine, individuals previously infected with COVID-19 have displayed immunity levels comparable to an uninfected person who has received both doses. In fact, in those previously infected, a single vaccine dose can boost the antibody response by up to 1,000-fold. This response is significantly higher than that of non-infected people who received two doses of an mRNA vaccine.
The Science
Two recent studies demonstrate the immunological and clinical benefits of getting vaccinated, even after having recovered from COVID-19.
The first, and most directly informative study, “Reduced Risk of Reinfection with SARS-CoV-2 After COVID-19 Vaccination — Kentucky, May–June 2021” was published August 6, 2021, in the “Morbidity and Mortality Weekly Report.” In this study, researchers cross-linked two state databases to identify those who tested positive for COVID-19 and later received a vaccine.
The study revealed that, of the 738 people who’d previously tested positive for COVID-19, 246 became reinfected between May and June of 2021. Those individuals were matched (for age, gender, and month of initial infection) to the 492 people who did not become reinfected during the same period. Of those who developed recurrent COVID-19 infections, nearly 73% had not received a vaccine, compared to only about 58% of those who did not become reinfected. This difference was highly statistically significant (P < 0.0001), with an odds ratio of 2.34 (95% confidence interval: 1.58-3.47).
Other laboratory evidence has suggested the antibody response to COVID-19 vaccination provides better protection against some circulating variants than does natural infection; this “real-world” epidemiologic finding supports the benefit of vaccination for those previously infected persons. The main public health message of this study? “To reduce their likelihood for future infection, all eligible persons should be offered COVID-19 vaccine, even those with previous SARS-CoV-2 infection.”
Also, the “Journal of the American Medical Association” recently published the finding that SARS CoV-2 antibody responses against the SARS-CoV-2 spike protein were significantly stronger in 29 people who were previously infected and then given the Pfizer/BioNTech vaccine, compared to those from 30 other vaccinated people who were not previously infected.
A third recently reported cohort consisted of 63 people who recovered from COVID-19 infection, of whom 41% later received an mRNA vaccine. All had blood drawn for laboratory assessment of their immune status against SARS-CoV-2. Several measures of humoral immunity and protective B-cell memory were significantly greater in those who received the vaccine compared to those who did not receive the vaccine after the initial infection.
They concluded that “convalescent individuals who receive available mRNA vaccines will produce antibodies and memory B-cells that should be protective against circulating SARS-CoV-2 variants.” (Wang Z, Muecksch F, Schaefer-Babajew D, et al. Naturally enhanced neutralizing breadth against SARS-CoV-2 one year after infection. Nature. 2021;595:426-31. Doi: 10.1038/s41586-021-03696-9).
Hybrid Vigor Immunity
The immunity boost accompanying infection and vaccination works much like the hybrid vigor that produces the Cosmic Crisp apple.
By crossing Honeycrisp and Enterprise apple varieties, apple growers achieve the texture and juiciness of the Honeycrisp and the late-ripening behavior and long storage of the Enterprise. The hybrid vigor immunity from infection and vaccination will potentially be in play for an important percentage of the population.
What Makes the Vaccine More Effective?
COVID-19 vaccines educate our immune systems to make specific antibodies against the virus’ spike protein. These antibodies are considerably lower in approximately one-third of individuals following just infection and even lower in those who’ve experienced less severe disease, as well as in younger individuals.
Community Immunity
When enough people are vaccinated, a phenomenon known as “community immunity” develops.
Community immunity helps to protect the more vulnerable members of our community by limiting the deadly virus’ ability to spread. It also functions to protect the integrity of our health systems, our infrastructure, and supply chains, and more importantly protects the minds, bodies, and spirits of our healthcare workers who are our frontline soldiers in this fight. Vaccines can also protect us from other virally induced diseases that can be initiated by infections, such as cancer and autoimmune diseases.
What About the Variants?
Immunity from infection has been shown to produce an antibody response that is variable against the emerging COVID virus variants, including the beta, gamma, and delta variants. In some cases, the antibodies generated by infection may not be as effective at blocking re-infection from these variants, with an observed reduction of antibody recognition.
COVID vaccines, however, deliver a standardized dose of the protective immunity stimulators. Those who receive a vaccine have a much more consistent number of immune cells. In fact, the vaccines currently authorized in the United States continue to demonstrate impressive effectiveness against severe disease and death in both clinical trials as well as in “real-world” use. This has been true for the first stain of SARS CoV-2 and for the new variants.
In a Nutshell
COVID-19 vaccines protect against not only infection but reinfection by SARS CoV-2 and its known variants.
Written by Kimberly Taylor, Ph.D., William Elliott, M.D., Ph.D., Albert Brady, M.D., and Julie Randolph-Habecker, Ph.D.