Some viral vaccines are so good that they can prevent even mild illness for decades and eliminate the virus from the face of the earth. Others are good at protecting against serious disease, but not as good at protecting against mild disease or spread. The difference has nothing to do with the intelligence of the scientists who invented the vaccines or the competence of the companies that made them. Rather, the effectiveness of vaccines is largely determined by one thing: the incubation period of the disease, which is the time between exposure to a virus and the onset of symptoms.
If incubation periods are long—meaning a couple of weeks, as for smallpox, measles, and German measles (rubella)—then the virus can be eliminated from the face of the earth. If incubation periods are short—meaning only a few days as for SARS-CoV-2, influenza, respiratory syncytial virus, and common cold viruses—then the virus is likely to circulate for centuries causing mild illness in most and severe disease in some.
Why do incubation periods determine the effectiveness of a vaccine?
The key determinant for protection against mild illness is the level of virus-specific antibodies present at the time of exposure to the virus. The good news is that these antibodies are readily induced by natural infection or vaccination. The bad news is that they don’t last very long—usually 3 to 6 months—before they fade away. Therefore, for diseases with short incubation periods, protection against mild illness is always short-lived. Always.
SARS-CoV-2 vaccines are a perfect example of what you can expect from antibodies. When researchers from Pfizer and Moderna presented the results of their mRNA vaccine trials in December 2020, they showed that two doses induced 95 percent protection against both mild and severe disease. Why was protection against mild illness so high? The answer is that these studies were performed over a 3-month period; most of the participants had just received their second dose. For that reason, everyone still had high levels of antibodies in their bloodstream and, therefore, were protected against mild disease.
But protection against mild illness couldn’t last.
By the middle of 2021, about 6 months after people had received their second dose of vaccine—when antibodies had begun to decline—protection against mild illness had also declined from 95 percent to 50 percent.
Protection against severe illness, on the other hand, had remained high. That’s because protection against severe illness isn’t dependent on antibodies present at the time of exposure; it’s dependent on immune memory cells, like memory B cells, which can be stimulated to make antibodies. The good news about these immune memory cells is that they are long-lived, often for decades. The bad news is that it takes time after exposure to the virus for these memory cells to become activated and to make antibodies.
For diseases with short incubation periods, like COVID, symptoms begin before these memory B cells have had enough time to make antibodies. Therefore, people suffer mild illness. On the other hand, it takes much longer—about a couple of weeks—to develop severe COVID. That’s plenty of time for these memory B cells to become activated and to make antibodies to prevent severe disease. This is why protection against mild disease is short-lived and protection against severe disease is long-lived.
On the other hand, for diseases with long incubation periods, symptoms begin after memory B cells have had enough time to make antibodies that can prevent even mild illness and spread. This is why diseases with long incubation periods can be eliminated from the face of the earth.
Even if everyone in the world received a COVID vaccine, and SARS-CoV-2 virus didn’t form new variants, many people would still suffer mild disease and some severe disease every year. Like influenza virus, which has been around since the mid-1300s, it is unlikely that we will ever eliminate SARS-CoV-2 virus.
When the vaccines came out, I was first in line, being 77 years old. My experience was good. I got the vaccine just before the delta variant became widespread.
But here’s the thing that will haunt public health for years. I read, over and over, in many places, that the goal was herd immunity. And extinction of the virus. That was the justification for vaccination mandates. Now we find out that that goal was impossible, and epidemiologists knew this all along. Or should have.
This is going to cause problems if mandates are ever again attempted.
any comments about the cleveland clinic study? more covid jabs more covid infections...
https://academic.oup.com/ofid/advance-article/doi/10.1093/ofid/ofad209/7131292?login=false
complete manuscript: available at the link above...article is now 'peer reviewed'
ALL quotes below from the discussion section:
"The strengths of our study include its large sample size, and its conduct in a healthcare system
where a very early recognition of the critical importance of maintaining an effective workforce
during the pandemic led to devotion of resources to have an accurate accounting of who had
COVID-19, when COVID-19 was diagnosed, who received a COVID-19 vaccine, and when. The
study methodology, treating bivalent vaccination as a time-dependent covariate, allowed for
determining vaccine effectiveness in real time."
"our study was done in a healthcare population, and included no children and few elderly subjects, and the majority of study subjects would not have been immunocompromised."
"The association of increased risk of COVID-19 with higher numbers of prior vaccine doses was
unexpected. A simplistic explanation might be that those who received more doses were more
likely to be individuals at higher risk of COVID-19. A small proportion of individuals may have
fit this description. However, the majority of subjects in this study were generally young
individuals and all were eligible to have received at least 3 doses of vaccine by the study start date,
and which they had every opportunity to do. Therefore, those who received fewer than 3 doses
(46% of individuals in the study) were not those ineligible to receive the vaccine, but those who
chose not to follow the CDC’s recommendations on remaining updated with COVID-19
vaccination, and one could reasonably expect these individuals to have been more likely to have
exhibited higher risk-taking behavior. Despite this, their risk of acquiring COVID-19 was lower
than those who received a larger number of prior vaccine doses. This is not the only study to find
a possible association with more prior vaccine doses and higher risk of COVID-19."