#16,144
Last summer (see `Forward Looking' & `Aspirational' Vaccine Press Releases) and again last fall (see A COVID Vaccine Reality Check) - even though I am decidedly `pro-vaccine' - I wrote about the dangers of over-promising on the delivery, deployment, effectiveness, and ultimate impact of a COVID vaccine.
I'll be the first to admit that the COVID vaccine's creation, production, and effectiveness have exceeded my initial expectations. I went into 2021 quite happy if we only saw a 75% VE (vaccine Effectiveness) and 2 or 3 billion shots produced by summer.
Early on, the mRNA vaccines showed up to 90% effectiveness, and more than 5 billion doses have been administered in the first 10 months. A rousing success, even if it hasn't been enough to end the pandemic.
And that's the problem; people were primed to expect a quick resolution of this crisis once the vaccine was released. They were led to believe that vaccinated = fully protected, and that life would soon return to normal.
That was the message that politicians wanted, the economy arguably needed - and coupled with astoundingly good early VE results from clinical trial data against a relatively stable COVID virus - seemed almost possible last December.
But then Alpha upset those plans, only to be upstaged by Delta.
Whether due to the emergence of these new variants, a waning of vaccine induced immunity over time, or both - those early spectacular VE numbers against symptomatic infection have fallen to more expected values (50%-75%), although protection against severe illness, hospitalization, and death remain reassuringly high.
During any pandemic, we need to expect that the goal posts will be moved as the virus changes. What worked well in January may not work as well today, and there are no guarantees that what we do now will serve us well next spring.
Just as the virus continually adapts, so must we.
Despite these dropping numbers - and the apparent need for boosters sooner rather than later - these early vaccines continue to save lives, and reduce the burden on hospitals. The only true failure here was the inability of many governments to manage their public's expectations of what deployment of a vaccine would actually mean.
Yesterday the CDC published two Early Release MMWR reports, both of which reaffirm the protection against COVID offered by vaccination, while at the same time they show that protection is less robust today than it was 6 months ago.
The first shows that in Los Angeles between May 1st and July 25th - while 25% of all infections were among those fully vaccinated - you are 5 times more likely to be infected if you are unvaccinated, and 29.2 times more likely to hospitalized.
SARS-CoV-2 Infections and Hospitalizations Among Persons Aged ≥16 Years, by Vaccination Status — Los Angeles County, California, May 1–July 25, 2021
Early Release / August 24, 2021 / 70
Jennifer B. Griffin, PhD1; Meredith Haddix, MPH1; Phoebe Danza, MPH1; Rebecca Fisher, MPH1; Tae Hee Koo, MPH1; Elizabeth Traub, MPH1; Prabhu Gounder, MD1; Claire Jarashow, PhD2; Sharon Balter, MD1 (View author affiliations)View suggested citation
Summary
What is already known about this topic?
Although COVID-19 vaccines are highly effective, some fully vaccinated persons will be infected with SARS-CoV-2.
What is added by this report?
During May 1–July 25, 2021, among 43,127 SARS-CoV-2 infections in residents of Los Angeles County, California, 10,895 (25.3%) were in fully vaccinated persons, 1,431 (3.3%) were in partially vaccinated persons, and 30,801 (71.4%) were in unvaccinated persons. On July 25, infection and hospitalization rates among unvaccinated persons were 4.9 and 29.2 times, respectively, those in fully vaccinated persons. In July, when the Delta variant was predominant, cycle threshold values were similar for unvaccinated, partially vaccinated, and vaccinated persons.
What are the implications for public health practice?
Efforts to enhance COVID-19 vaccination coverage, in coordination with other prevention strategies, are critical to preventing COVID-19–related hospitalizations and deaths.
In other words, during a time when the goal posts were moving. It may take a few more months before we can fully appreciate the trends that began over the summer.
The second report looks at the effectiveness of the COVID vaccine in protecting healthcare workers both before and after the arrival of Delta across 8 locations. Once again we see a decline (from 91% VE) before Delta, to 66% VE after Delta became dominant.
How much of this VE decline is due to waning vaccine protection, and how much is due to the Delta variant, isn't clear. But even at 66%, the COVID vaccine provides valuable protection.
Effectiveness of COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Frontline Workers Before and During B.1.617.2 (Delta) Variant Predominance — Eight U.S. Locations, December 2020–August 2021
Early Release / August 24, 2021 / 70
Ashley Fowlkes, ScD1; Manjusha Gaglani, MBBS2; Kimberly Groover, PhD3; Matthew S. Thiese, PhD4; Harmony Tyner, MD5; Katherine Ellingson, PhD6; HEROES-RECOVER Cohorts (View author affiliations)
(Excerpt)
During the 35-week study period, 4,136 participants with no previous laboratory-documented SARS-CoV-2 infection contributed a median of 20 unvaccinated days per participant (interquartile range [IQR] = 8–45 days; total = 181,357 days), during which 194 SARS-CoV-2 infections were identified; 89.7% of these infections were symptomatic. A total of 2,976 participants contributed a median of 177 fully vaccinated days (IQR = 115–195 days; total = 455,175 days) with 34 infections, 80.6% of which were symptomatic.
Adjusted VE against SARS-CoV-2 infection was 80% (95% confidence interval [CI] = 69%–88%). The VE point estimate was 85% among participants for whom <120 days had elapsed since completion of full vaccination compared with 73% among those for whom ≥150 days had elapsed; however the VE 95% CI were overlapping, indicating the difference was not statistically significant (Table).
During Delta variant–predominant weeks at study sites, 488 unvaccinated participants contributed a median of 43 days (IQR = 37–69 days; total = 24,871 days) with 19 SARS-CoV-2 infections (94.7% symptomatic); 2,352 fully vaccinated participants contributed a median of 49 days (IQR = 35–56 days; total = 119,218 days) with 24 SARS-CoV-2 infections (75.0% symptomatic). Adjusted VE during this Delta predominant period was 66% (95% CI = 26%–84%) compared with 91% (95% CI = 81%–96%) during the months preceding Delta predominance.
During December 14, 2020–August 14, 2021, full vaccination with COVID-19 vaccines was 80% effective in preventing RT-PCR–confirmed SARS-CoV-2 infection among frontline workers, further affirming the highly protective benefit of full vaccination up to and through the most recent summer U.S. COVID-19 pandemic waves.The VE point estimates declined from 91% before predominance of the SARS-CoV-2 Delta variant to 66% since the SARS-CoV-2 Delta variant became predominant at the HEROES-RECOVER cohort study sites; however, this trend should be interpreted with caution because VE might also be declining as time since vaccination increases and because of poor precision in estimates due to limited number of weeks of observation and few infections among participants. As with all observational VE studies, unmeasured and residual confounding might be present. Active surveillance through the cohort is ongoing and VE estimates will be monitored continuously.Although these interim findings suggest a moderate reduction in the effectiveness of COVID-19 vaccines in preventing infection, the sustained two thirds reduction in infection risk underscores the continued importance and benefits of COVID-19 vaccination.
Over time, SARS-CoV-2 will probably loose some of its impact, either through an evolutionary attenuation of the virus, or the gradual build-up of community immunity, through a combination of vaccination and constant exposure.
Until that happens, vaccinations - even if their VE is less than we'd like - remain the best individual measure we can take to get us back to something approaching `normal'.
Assuming, of course, that enough people elect to get them.
