Credit ACIP/CDC
Among the arguments frequently seen on social media against getting the COVID vaccine - one of the most common insists that if you've already had a COVID infection - you are better protected than if you'd taken the vaccine.
While plausible, as with so many of these blanket declarations, evidence is never provided. This argument is predicated, I suppose, on the common belief that `natural is always better than artificial'.
Recent history suggests that may not be so - with the constant introduction of new variants - we've seen huge numbers of reinfections in places like Brazil (see The Lancet: Resurgence of COVID-19 in Manaus, Brazil, Despite High Seroprevalence), and research on other coronaviruses (see Nature Medicine: Seasonal Coronavirus Protective Immunity Is Short-Lasting), have demonstrated that natural immunity can be short lived.
In fairness, we've also seen breakthrough infections among the vaccinated, so neither provides complete protection. But the assumption that once you are infected and recovered you are immune to reinfection, is specious.
Reinfection data on the Delta variant - which has risen to dominance over the past couple of months - is just coming in, but today we have a early release from the CDC's MMWR that finds that among those who have been previously infected with COVID, those that are also vaccinated have a far lower risk of reinfection.
This study took place mostly during at a time (May-June 2021) when the Alpha variant peaked in the United States, and before Delta took full control (see CDC chart below).
I've only include the link, summary, and some extended excerpts from the report. Follow the link to read it in its entirety.
Reduced Risk of Reinfection with SARS-CoV-2 After COVID-19 Vaccination — Kentucky, May–June 2021
Early Release / August 6, 2021 / 70
Alyson M. Cavanaugh, DPT, PhD1,2; Kevin B. Spicer, MD, PhD2,3; Douglas Thoroughman, PhD2,4; Connor Glick, MS2; Kathleen Winter, PhD2,5 (View author affiliations)View suggested citation
SummaryWhat is already known about this topic?Reinfection with human coronaviruses, including SARS-CoV-2, the virus that causes COVID-19, has been documented. Currently, limited evidence concerning the protection afforded by vaccination against reinfection with SARS-CoV-2 is available.What is added by this report?Among Kentucky residents infected with SARS-CoV-2 in 2020, vaccination status of those reinfected during May–June 2021 was compared with that of residents who were not reinfected. In this case-control study, being unvaccinated was associated with 2.34 times the odds of reinfection compared with being fully vaccinated.What are the implications for public health practice?To reduce their likelihood for future infection, all eligible persons should be offered COVID-19 vaccine, even those with previous SARS-CoV-2 infection.
Related Materials
Although laboratory evidence suggests that antibody responses following COVID-19 vaccination provide better neutralization of some circulating variants than does natural infection (1,2), few real-world epidemiologic studies exist to support the benefit of vaccination for previously infected persons.This report details the findings of a case-control evaluation of the association between vaccination and SARS-CoV-2 reinfection in Kentucky during May–June 2021 among persons previously infected with SARS-CoV-2 in 2020.
Kentucky residents who were not vaccinated had 2.34 times the odds of reinfection compared with those who were fully vaccinated (odds ratio [OR] = 2.34; 95% confidence interval [CI] = 1.58–3.47).
These findings suggest that among persons with previous SARS-CoV-2 infection, full vaccination provides additional protection against reinfection. To reduce their risk of infection, all eligible persons should be offered vaccination, even if they have been previously infected with SARS-CoV-2.*
(SNIP)
DiscussionThis study found that among Kentucky residents who were previously infected with SARS-CoV-2 in 2020, those who were unvaccinated against COVID-19 had significantly higher likelihood of reinfection during May and June 2021. This finding supports the CDC recommendation that all eligible persons be offered COVID-19 vaccination, regardless of previous SARS-CoV-2 infection status.Reinfection with SARS-CoV-2 has been documented, but the scientific understanding of natural infection-derived immunity is still emerging (5). The duration of immunity resulting from natural infection, although not well understood, is suspected to persist for ≥90 days in most persons.** The emergence of new variants might affect the duration of infection-acquired immunity, and laboratory studies have shown that sera from previously infected persons might offer weak or inconsistent responses against several variants of concern (2,6).
For example, a recent laboratory study found that sera collected from previously infected persons before they were vaccinated provided a relatively weaker, and in some cases absent, neutralization response to the B.1.351 (Beta) variant when compared with the original Wuhan-Hu-1 strain (1). Sera from the same persons after vaccination showed a heightened neutralization response to the Beta variant, suggesting that vaccination enhances the immune response even to a variant to which the infected person had not been previously exposed.Although such laboratory evidence continues to suggest that vaccination provides improved neutralization of SARS-CoV-2 variants, limited evidence in real-world settings to date corroborates the findings that vaccination can provide improved protection for previously infected persons. The findings from this study suggest that among previously infected persons, full vaccination is associated with reduced likelihood of reinfection, and, conversely, being unvaccinated is associated with higher likelihood of being reinfected.
The lack of a significant association with partial versus full vaccination should be interpreted with caution given the small numbers of partially vaccinated persons included in the analysis (6.9% of case-patients and 7.9% of controls), which limited statistical power. The lower odds of reinfection among the partially vaccinated group compared with the unvaccinated group is suggestive of a protective effect and consistent with findings from previous studies indicating higher titers after the first mRNA vaccine dose in persons who were previously infected (7,8).(SNIP - Limitations)These findings suggest that among persons with previous SARS-CoV-2 infection, full vaccination provides additional protection against reinfection. Among previously infected Kentucky residents, those who were not vaccinated were more than twice as likely to be reinfected compared with those with full vaccination. All eligible persons should be offered vaccination, including those with previous SARS-CoV-2 infection, to reduce their risk for future infection.
New CDC Study: Vaccination Offers Higher Protection than Previous COVID-19 Infection
While I doubt there is any amount of scientific data that will convince hardcore vaccine skeptics, hopefully - for those merely on the fence about getting vaccinated - this study might provide some additional impetus.
While this certainly won't be the last word on the subject - and new variants could change the equation - those of us who are both fully vaccinated and previously had a bout with the virus can probably take some degree of comfort in the fact that we may be more protected as a result.
