#16,284
Despite a dearth of supporting evidence, 18 months ago many governments (and more than a few scientists) were promoting the idea that `herd' immunity - at the time, achievable only through natural infection - would be our way out of the COVID Pandemic.
Once we'd reached some (undetermined) percentage of acquired community immunity, the assumption was the pandemic would end and life would return to normal.
The `fly in this ointment' was - while there are indeed many viral infections which leave behind long-lasting (or even permanent) immunity - it is far from being universally true. And we'd seen evidence in the past suggesting that coronaviruses might be less than accommodating.
In Fenner and White's Medical Virology (Fifth Edition - 2017),, the authors described the clinical features of seasonal human coronaviruses (hCoVs) in Chapter 31:
The typical coronavirus “common cold” is mild and the virus remains localized to the epithelium of the upper respiratory tract and elicits a poor immune response, hence the high rate of reinfection. There is no cross-immunity between human coronavirus-229E and human coronavirus-OC43, and it is likely that new strains are continually arising by mutation selection.
Perhaps more on point, in 2016's EID Journal: Antibody Response & Disease Severity In HCW MERS Survivors, we looked at a study that tested 9 Health care workers who were infected during the 2014 Jeddah outbreak (2 severe pneumonia, 3 milder pneumonia, 1 URTI, and 3 asymptomatic), that found only those with severe pneumonia still carried detectable levels of antibodies 18 months later.
Those who experienced a milder pneumonia had shorter lived antibody responses (1 out to 10 months, 2 out to 3 months), while the URTI and asymptomatic cases tested negative at 3 months post infection.
By the end of 2020 - even before the vaccine was rolled out - some nations we're reporting a high enough seroprevalence rate to suggest that their risks of seeing a major winter wave were declining rapidly.
One of them was Brazil, which had seen a huge pandemic wave in the spring, but began to report massive surges of the pandemic virus last December. This, despite their population presumably having a high degree of `acquired immunity' (see The Lancet: Resurgence of COVID-19 in Manaus, Brazil, Despite High Seroprevalence).
Hopes gradually shifted from naturally acquired immunity, to vaccination. But as we now know - while they offer excellent initial protection, particularly against severe disease, hospitalization, and death - their protective effect appears to wane over 6 to 8 months, requiring booster shots.
With neither being a perfect or permanent solution, the question becomes: Which is more protective? Getting the vaccine, or `natural' post-infection immunity?
While many people are still convinced that `natural immunity' is somehow superior to the vaccine, yesterday the CDC's MMWR published a report strongly suggesting that previously infected individuals were 5.5 times more likely to be reinfected with Delta than a vaccinated person was to have a breakthrough infection.
And that number increases dramatically for those over the age of 60.
First the link, summary, and some excerpts from the MMWR report, then I'll have a bit more.
Laboratory-Confirmed COVID-19 Among Adults Hospitalized with COVID-19–Like Illness with Infection-Induced or mRNA Vaccine-Induced SARS-CoV-2 Immunity — Nine States, January–September 2021
Early Release / October 29, 2021 / 70
Catherine H. Bozio, PhD1; Shaun J. Grannis, MD2,3; Allison L. Naleway, PhD4; Toan C. Ong, PhD5; Kristen A. Butterfield, MPH6; Malini B. DeSilva, MD7; Karthik Natarajan, PhD8,9; Duck-Hye Yang, PhD6; Suchitra Rao, MBBS5; Nicola P. Klein, MD, PhD10; Stephanie A. Irving, MHS4; Brian E. Dixon, PhD2,11; Kristin Dascomb, MD, PhD12; I-Chia Liao, MPH13; Sue Reynolds, PhD1; Charlene McEvoy, MD7; Jungmi Han8; Sarah E. Reese, PhD6; Ned Lewis, MPH10; William F. Fadel, PhD2,11; Nancy Grisel, MPP12; Kempapura Murthy, MBBS13; Jill Ferdinands, PhD1; Anupam B. Kharbanda, MD14; Patrick K. Mitchell, ScD6; Kristin Goddard, MPH10; Peter J. Embi, MD3,15; Julie Arndorfer, MPH12; Chandni Raiyani, MPH13; Palak Patel, MBBS1; Elizabeth A. Rowley, DrPH6; Bruce Fireman, MA10; Nimish R. Valvi, DrPH, MBBS2; Eric P. Griggs, MPH1; Matthew E. Levy, PhD6; Ousseny Zerbo, PhD10; Rachael M. Porter, MPH1; Rebecca J. Birch, MPH6; Lenee Blanton, MPH1; Sarah W. Ball, ScD6; Andrea Steffens, MPH1; Natalie Olson, MPH1; Jeremiah Williams, MPH1; Monica Dickerson, MPH1; Meredith McMorrow, MD1; Stephanie J. Schrag, DPhil1; Jennifer R. Verani, MD1; Alicia M. Fry, MD1; Eduardo Azziz-Baumgartner, MD1; Michelle Barron, MD5; Manjusha Gaglani, MBBS13; Mark G. Thompson, PhD1; Edward Stenehjem, MD12 (View author affiliations)View suggested citation
Summary
What is already known about this topic?
Previous infection with SARS-CoV-2 or COVID-19 vaccination can provide immunity and protection against subsequent SARS-CoV-2 infection and illness.
What is added by this report?
Among COVID-19–like illness hospitalizations among adults aged ≥18 years whose previous infection or vaccination occurred 90–179 days earlier, the adjusted odds of laboratory-confirmed COVID-19 among unvaccinated adults with previous SARS-CoV-2 infection were 5.49-fold higher than the odds among fully vaccinated recipients of an mRNA COVID-19 vaccine who had no previous documented infection (95% confidence interval = 2.75–10.99).
What are the implications for public health practice?
All eligible persons should be vaccinated against COVID-19 as soon as possible, including unvaccinated persons previously infected with SARS-CoV-2.
(SNIP)
Discussion
In this multistate analysis of hospitalizations for COVID-19–like illness among adults aged ≥18 years during January–September 2021 whose previous infection or vaccination occurred 90–179 days earlier, the adjusted odds of laboratory-confirmed COVID-19 were higher among unvaccinated and previously infected patients than among those who were fully vaccinated with 2 doses of an mRNA COVID-19 vaccine without previous documentation of a SARS-CoV-2 infection. Secondary analyses that did not adjust for time since infection or vaccination or adjusted time since infection or vaccination differently as well as before and during Delta variant predominance produced similar results.
These findings are consistent with evidence that neutralizing antibody titers after receipt of 2 doses of mRNA COVID-19 vaccine are high (5,6); however, these findings differ from those of a retrospective records-based cohort study in Israel,†† which did not find higher protection for vaccinated adults compared with those with previous infection during a period of Delta variant circulation. This variation is possibly related to differences in the outcome of interest and restrictions on the timing of vaccination. The Israeli cohort study assessed any positive SARS-CoV-2 test result, whereas this study examined laboratory-confirmed COVID-19 among hospitalized patients. The Israeli cohort study also only examined vaccinations that had occurred 6 months earlier, so the benefit of more recent vaccination was not examined. This report focused on the early protection from infection-induced and vaccine-induced immunity, though it is possible that estimates could be affected by time. Understanding infection-induced and vaccine-induced immunity over time is important, particularly for future studies to consider.
In this study, the benefit of vaccination compared with infection without vaccination appeared to be higher for recipients of Moderna than Pfizer-BioNTech vaccine, which is consistent with a recent study that found higher vaccine effectiveness against COVID-19 hospitalizations for Moderna vaccine recipients than for Pfizer-BioNTech vaccine recipients (7).
In this study, the protective effect of vaccination also trended higher for adults aged ≥65 years than for those aged 18–64 years. However, considering the limited data by both product type and age, additional research is needed on the relative protection of vaccination versus infection without vaccination across demographic groups and vaccine products, as well as vaccination in previously infected persons.
The findings in this report are subject to at least seven limitations.
- First, although this analysis was designed to compare two groups with different sources of immunity, patients might have been misclassified. If SARS-CoV-2 testing occurred outside of network partners’ medical facilities or if vaccinated persons are less likely to seek testing, some positive SARS-CoV-2 test results might have been missed and thus some patients classified as vaccinated and previously uninfected might also have been infected. In addition, despite the high specificity of COVID-19 vaccination status from these data sources, misclassification is possible.
- Second, the aOR could not be further stratified by time since infection or vaccination because of sparse data and limited ability to control for residual confounding that could be magnified within shorter intervals. The aOR that did not adjust for time might also be subject to residual confounding, particularly related to waning of both types of immunity.
- Third, selection bias might be possible if vaccination status influences likelihood of testing and if previous infection influences the likelihood of vaccination. Previous work from the VISION network did not identify systematic bias in testing by vaccination status, based on data through May 2021 (1).
- Fourth, residual confounding might exist because the study did not measure or adjust for behavioral differences between the comparison groups that could modify the risk of the outcome.
- Fifth, these results might not be generalizable to nonhospitalized patients who have different access to medical care or different health care–seeking behaviors, particularly outside of the nine states covered.
- Sixth, the statistical model incorporated the use of a weighted propensity score method which is subject to biases in estimates or standard errors if the propensity score model is misspecified. Numerous techniques were used to reduce potential suboptimal specification of the model, including but not limited to including a large set of covariates for machine learning estimation of propensity scores, including covariates in both regression and propensity models, ensuring large sample sizes and checking stability of weights, and conducting secondary analyses to assess robustness of results.
- Finally, the study assessed COVID-19 mRNA vaccines only; findings should not be generalized to the Janssen vaccine.
In this U.S.-based epidemiologic analysis of patients hospitalized with COVID-19–like illness whose previous infection or vaccination occurred 90–179 days earlier, vaccine-induced immunity was more protective than infection-induced immunity against laboratory-confirmed COVID-19, including during a period of Delta variant predominance. All eligible persons should be vaccinated against COVID-19 as soon as possible, including unvaccinated persons previously infected with SARS-CoV-2.
There are admittedly limitations to this study (as there are all all studies), but this is pretty compelling evidence; Vaccination against COVID provides superior protection compared to `natural' post-infection immunity'.
While far from perfect, COVID vaccines are also far safer than getting immunity via infection, sparing the recipient the known risks of severe illness, hospitalization, potential `Long COVID' sequelae, or even death.
While both mRNA vaccines provided superior protection vs. naturally acquired immunity, the data suggests that Moderna vaccine outperformed Pfizer. Due to sparse data, patients who received the J&J Janssen vaccine were excluded from this study.
Finally, the CDC released the following statement on this MMWR report yesterday afternoon.
New CDC Study: Vaccination Offers Higher Protection than Previous COVID-19 Infection
Study participants were over 5 times more likely to have COVID-19 if they were unvaccinated and had a prior infection
Media Statement
Embargoed Until: Friday, October 29, 2021, 1:00 p.m. ET
Contact: Media Relations
(404) 639-3286
Today, CDC published new science reinforcing that vaccination is the best protection against COVID-19. In a new MMWR examining more than 7,000 people across 9 states who were hospitalized with COVID-like illness, CDC found that those who were unvaccinated and had a recent infection were 5 times more likely to have COVID-19 than those who were recently fully vaccinated and did not have a prior infection.
The data demonstrate that vaccination can provide a higher, more robust, and more consistent level of immunity to protect people from hospitalization for COVID-19 than infection alone for at least 6 months.
“We now have additional evidence that reaffirms the importance of COVID-19 vaccines, even if you have had prior infection. This study adds more to the body of knowledge demonstrating the protection of vaccines against severe disease from COVID-19. The best way to stop COVID-19, including the emergence of variants, is with widespread COVID-19 vaccination and with disease prevention actions such as mask wearing, washing hands often, physical distancing, and staying home when sick,” said CDC Director Dr. Rochelle P. Walensky.
The study looked at data from the VISION Network that showed among adults hospitalized with symptoms similar to COVID-19, unvaccinated people with prior infection within 3-6 months were 5.49 times more likely to have laboratory-confirmed COVID-19 than those who were fully vaccinated within 3-6 months with mRNA (Pfizer or Moderna) COVID-19 vaccines. The study was conducted across 187 hospitals.
COVID-19 vaccines are safe and effective. They prevent severe illness, hospitalization, and death. CDC continues to recommend everyone 12 and older get vaccinated against COVID-19.
The evidence continues to mount that vaccines - along with appropriate boosters over time - are our best options for bringing COVID under control. Even then, the coronavirus isn't likely to go away completely, but over time, it should become more of a seasonal threat, like influenza.
