On COVID-19
This is from an old friend, Peter Spitzer, MD (pictured), a fellow alumnus of the William Penn Charter School, class of 1973, who went on to specialize in infectious diseases. I feel fortunate to be a part of a monthly Zoom call in which he normally provides an update on COVID and all the related subjects: vaccine efficacy, mask-wearing, new variants, spreading patterns, lethality, CDC response, best practices, etc.
As this risk of sounding snotty, given his credentials (below) I put far more credence in what he says than I do in car salesmen, baseball coaches, building contractors, congressional Republicans, and the like.
The subject line from Peter’s email reads: “Suffering from insomnia? Read this and it will put you right out.” He has a point, as you’ll see.
I wanted to follow-up our discussion from yesterday about Covid-19 infection and Covid vaccine efficacy. To better understand this, it is helpful to add a little historical perspective. Covid-19 infection was first described in China in December 2019. There was a lot of data suppression by the Chinese government and thus the details are somewhat sketchy. Nonetheless, the first case described in the United States was in January 2020. Incredibly, we had two new mRNA vaccines for this brand-new pathogen and illness by December 2020 when they were released in the United States under an emergency use authorization (EUA).
Data from the clinical trials on these vaccines were published late in 2020 and in 2021. Both the Pfizer and Moderna vaccines looked incredibly effective at preventing symptomatic Covid infection. The original 2 dose series prevented symptomatic Covid at two months by roughly 90-100%, depending on age, vaccine type, and comorbid conditions. The vaccine efficacy (VE) decreased to somewhere between 84-93% at 6 months. However, the efficacy of these vaccines in preventing hospitalizations and serious disease was greater than 90%. This was at a time early in the history of this disease when variants were not prevalent. In fact, during the first year of this Covid outbreak, the evolution of this virus and variants was very slow paced and not really clinically relevant.
Newer Covid variants of concern started to occur later in 2021 which resulted in decreased VE. Many of the new lineages evaded vaccine induced immunity. The first major variant of concern was the Delta variant which became quite prominent during the summer of 2021. The Delta variant gave way to the Omicron variant in December 2021. After that, newer forms of Omicron variants have emerged (BA.1 giving way to BA.2, then BA.3, etc). Coronavirus neutralizing antibody titers, induced by the vaccine, were lower against the Delta variant and substantially lower against the Omicron variant, when compared with the activity against the early circulating strains. This helps to explain why monoclonal antibody treatments were released and then became ineffective after several months of use.
Since the original studies in 2020, VE against just symptomatic disease (as opposed to hospitalizations) has been assessed largely by observational study. The observed effectiveness of Covid vaccines for preventing symptomatic disease seems to have decreased over time from the original fantastic numbers in the clinical trials in 2020 when only the Covid-19 original strain was circulating. Thankfully, the efficacy of these vaccines against serious disease was better preserved, although not as great as with the earlier virus strains.
A common metric used now to evaluate VE is hospitalizations.
Initially the efficacy against earlier variants was somewhat preserved. However, over time, the VE against Omicron variants has been decreasing. In part, this led to the new bivalent vaccine being released a few months ago containing the original strain and an Omicron strain. The hope is that the new vaccine will be a better fit for protection against strains actually circulating now.
In addition to the problems of new variants causing decreased VE, we also saw a drop in VE as people got farther away in time from their last vaccine. The CDC reported in February 2022 that vaccine effectiveness against Covid-19 associated hospitalizations was higher after the third dose then after the second dose, but waned with time since vaccination. During the early Omicron predominant period, VE against Covid-19 associated hospitalizations was 91% during the 2 months after a third dose, but decreased to 78% by the fourth month after a third dose. They added that the protection against hospitalizations exceeded that against milder disease including even emergency room visits. In October 2022, a report in Lancet ID suggested that against the predominant vaccine strains during the summer of 2022 (BA.4/BA.5), VE for preventing hospitalization was 73% if the third dose was received <6 months previously, but only 38% if the third vaccine dose was given > 6 months previously. They added that the VE for milder outcomes was <50% if the third vaccine dose had been given > 6 months previously. VE for milder illness was only >50% in the first 3 months after receiving the third vaccine.
As you can see, both the increasing resistance to the Covid vaccines with subsequent variants and the decrease in VE as we get farther away from our last vaccine, help explain the concept of “breakthrough infection.”
So, one might ask, why even get a vaccine? I would say that some protection is better than no protection. We only have to look at the track record of the yearly Influenza vaccine (flu shot). I would bet that most, if not all, of us get a flu shot every year. However, the VE for preventing Influenza varies from year to year. Nonetheless, at best, it is 40-60% effective. Some years it is much less.
On a different topic, I know we are talking about masks. We all agree that they are effective in preventing the spread of coronavirus infection. However as everyone knows, they can also be effective in preventing the spread of Influenza and other viral infections. My own personal feeling is that private entities should be allowed to impose mask mandates, whether they be dinner parties in the home, entering physician offices or hospitals, private clubs, etc. Nonetheless, in other circumstances, my hope is that barring any serious epidemics or emergency situations, no one should be shamed whether they do, or do not, wear a mask.
Wishing everyone well, Peter
