#16,184
Following the euphoric, and frankly unrealistic, predictions of COVID vaccine effectiveness (95%) last winter, this summer's reality is no doubt disappointing to many. Breakthrough infections from Delta - which are increasing over time - have provided fodder for the anti-vaccine brigade's propaganda machine, and have raised doubts across the wider public.
No, the vaccines aren't perfect. They appear to lose effectiveness over time, and are certainly less effective against the Delta variant. Booster shots appear needed to sustain their effectiveness , and reformulations may be required down the road to deal with new variants.
Still, they provide valuable protection against severe illness, and reduce the odds of being infected at all. Not unlike the protection we see every year from flu vaccines. Given the increased lethality of COVID over seasonal flu, and the complications of `Long Covid', that makes them worth getting.
While no amount of data is likely to convince those who are convinced that the vaccine is `poison', or part of some nefarious global `depopulation' plan (yes, I've heard both), the data continues to support the continued uptake of the vaccine.
On Friday the CDC published a new MMWR report showing the vaccine's effectiveness over the summer against the Delta variant. While not as protective against breakthrough infection as we might desire, if your goal is to stay out of the hospital and not to die, the vaccines do a pretty good job.
Monitoring Incidence of COVID-19 Cases, Hospitalizations, and Deaths, by Vaccination Status — 13 U.S. Jurisdictions, April 4–July 17, 2021
Early Release / September 10, 2021 / 70
Heather M. Scobie, PhD1; Amelia G. Johnson, DrPH1; Amitabh B. Suthar, PharmD2; Rachel Severson, MS3; Nisha B. Alden, MPH3; Sharon Balter, MD4; Daniel Bertolino, MPH5; David Blythe, MD6; Shane Brady, MPH7; Betsy Cadwell, MSPH1; Iris Cheng, MS5; Sherri Davidson, PhD8; Janelle Delgadillo9; Katelynn Devinney, MPH5; Jeff Duchin, MD10; Monique Duwell, MD6; Rebecca Fisher, MPH4; Aaron Fleischauer, PhD11; Ashley Grant, MPH12; Jennifer Griffin, PhD4; Meredith Haddix, MPH4; Julie Hand, MSPH12; Matt Hanson, MD10; Eric Hawkins, MS13; Rachel K. Herlihy, MD3; Liam Hicks, MPH7; Corinne Holtzman, MPH14; Mikhail Hoskins, MPH11; Judie Hyun, MHS6; Ramandeep Kaur, PhD8; Meagan Kay, DVM10; Holly Kidrowski, MPH14; Curi Kim, MSPH6; Kenneth Komatsu, MPH7; Kiersten Kugeler, PhD1; Melissa Lewis, MPH1; B. Casey Lyons, MPH2; Shelby Lyons, MPH12; Ruth Lynfield, MD14; Keegan McCaffrey7; Chelsea McMullen, MS15; Lauren Milroy, MPH13; Stephanie Meyer, MPH14; Leisha Nolen, MD9; Monita R. Patel, PhD1; Sargis Pogosjans, MPH10; Heather E. Reese, PhD1; Amy Saupe, MPH14; Jessica Sell, MPH5; Theresa Sokol, MPH12; Daniel Sosin, MD15; Emma Stanislawski, MPH15; Kelly Stevens, MS8; Hailey Vest, MPH13; Kelly White, MPH13; Erica Wilson, MD11; Adam MacNeil, PhD1; Matthew D. Ritchey2; Benjamin J. Silk, PhD1 (View author affiliations)View suggested citation
Summary
What is already known about this topic?
The incidence of SARS-CoV-2 infection, hospitalization, and death is higher in unvaccinated than vaccinated persons, and the incidence rate ratios are related to vaccine effectiveness.
What is added by this report?
Across 13 U.S. jurisdictions, incidence rate ratios for hospitalization and death changed relatively little after the SARS-CoV-2 B.1.617.2 (Delta) variant reached predominance, suggesting high, continued vaccine effectiveness against severe COVID-19. Case IRRs decreased, suggesting reduced vaccine effectiveness for prevention of SARS-CoV-2 infections.
What are the implications for public health practice?
Getting vaccinated protects against severe illness from COVID-19, including the Delta variant. Monitoring COVID-19 incidence by vaccination status might provide early signals of potential changes in vaccine effectiveness that can be confirmed through robust controlled studies.
COVID-19 vaccine breakthrough infection surveillance helps monitor trends in disease incidence and severe outcomes in fully vaccinated persons, including the impact of the highly transmissible B.1.617.2 (Delta) variant of SARS-CoV-2, the virus that causes COVID-19. Reported COVID-19 cases, hospitalizations, and deaths occurring among persons aged ≥18 years during April 4–July 17, 2021, were analyzed by vaccination status across 13 U.S. jurisdictions that routinely linked case surveillance and immunization registry data.
Averaged weekly, age-standardized incidence rate ratios (IRRs) for cases among persons who were not fully vaccinated compared with those among fully vaccinated persons decreased from 11.1 (95% confidence interval [CI] = 7.8–15.8) to 4.6 (95% CI = 2.5–8.5) between two periods when prevalence of the Delta variant was lower (<50% of sequenced isolates; April 4–June 19) and higher (≥50%; June 20–July 17), and IRRs for hospitalizations and deaths decreased between the same two periods, from 13.3 (95% CI = 11.3–15.6) to 10.4 (95% CI = 8.1–13.3) and from 16.6 (95% CI = 13.5–20.4) to 11.3 (95% CI = 9.1–13.9).
Findings were consistent with a potential decline in vaccine protection against confirmed SARS-CoV-2 infection and continued strong protection against COVID-19–associated hospitalization and death. Getting vaccinated protects against severe illness from COVID-19, including the Delta variant, and monitoring COVID-19 incidence by vaccination status might provide early signals of changes in vaccine-related protection that can be confirmed through well-controlled vaccine effectiveness (VE) studies.
(SNIP)
Discussion
In 13 U.S. jurisdictions, rates of COVID-19 cases, hospitalizations, and deaths were substantially higher in persons not fully vaccinated compared with those in fully vaccinated persons, similar to findings in other reports (2,3). After the week of June 20, 2021, when the SARS-CoV-2 Delta variant became predominant, the percentage of fully vaccinated persons among cases increased more than expected for the given vaccination coverage and a constant VE. The IRR for cases among persons not fully vaccinated versus fully vaccinated decreased substantially; IRRs for hospitalizations and deaths changed less overall, but moderately among adults aged ≥65 years. Findings from this crude analysis of surveillance data are consistent with recent studies reporting decreased VE against confirmed infection but not hospitalization or death, during a period of Delta variant predominance and potential waning of vaccine-induced population immunity (4–6).†††
The findings in this report are subject to at least five limitations. First, combining unvaccinated and partially vaccinated persons resulted in lower IRR and VE estimates. Second, variable linkage of case surveillance, vaccination, hospitalization, and mortality data might have resulted in misclassifications that could influence IRR estimates; no substantial differences in ascertainment of outcomes by vaccination status were noted in jurisdictions that were able to assess this. Lags in reporting of deaths might have affected the second period differentially. Third, this was an ecological study in which IRRs lacked multivariable adjustments and causality could not be assessed (i.e., possible differences in testing or behaviors in vaccinated and unvaccinated persons). VE is being assessed through ongoing controlled studies. Fourth, the period when the SARS-CoV-2 Delta variant reached ≥50% overall prevalence was assumed to be the first week when most cases were infected with the Delta variant, but the week varied by jurisdiction. Finally, the data assessed from 13 jurisdictions accounted for 25% of the U.S. population, and therefore might not be generalizable.
Monitoring COVID-19 outcomes in populations over time by vaccination status is facilitated through reliable linkage of COVID-19 case surveillance and vaccination data. However, interpreting state-level variation by week might be challenging, especially for severe outcomes with small numbers. The framework used in this analysis allows for comparisons of observed IRRs and percentages of vaccinated cases, hospitalizations, and deaths to expected values. The data might be helpful in communicating the real-time impact of vaccines (e.g., persons not fully vaccinated having >10 times higher COVID-19 mortality risk) and guiding prevention strategies, such as vaccination and nonpharmacologic interventions.
Given the trends we've seen, I would not be surprised to see breakthrough infections increase as protection from the original vaccine wanes over time. Should Beta, Mu, Kappa, or one of the other emerging variants take a bigger role, that may further degrade the effectiveness of the vaccine.
And the 10-fold protection the vaccine appears to give today against hospitalization and/or death may begin to erode over time as well.
Despite these limitations, and the likely need for boosters and/or new vaccine formulations sooner rather than later, I'm quite happy to have been afforded the protection I've received from the vaccine. I never expected perfection, and warned repeatedly last year (see here, here, and here) against over-hyping the benefits of the vaccine, writing:
I've always believed it is better to under-promise and over-deliver, than the other way around. Things happen, plans go astray, and sometimes the wheels fall off. The more you promise, the less tolerance there will be for failure.
While the COVID vaccine is far from being a failure, its reputation now suffers due to the unrealistic expectations that were touted last winter. Hopefully, given the uncertainties of what COVID could throw at us next, we won't repeat that mistake promoting the booster shots this winter.
