COVID-19 immunity CANNOT be explained as “on or off” (like a light switch). It should be looked at more as a “dimmer switch”.

The conversation must change. COVID-19 immunity is NOT simply “vaccinated or not vaccinated”. We agree that to conquer the disease (or at least to keep people out of the hospital), categorizing people as “vaccinated or not” may be the only way to make and enforce policy decisions. However, the USA is now in a COVID-19 breakthrough spin cycle. At some point, the main question will be “How much immunity do you have – or need?” – a SPECTRUM. Not simply “Are you vaccinated or not?”.


The issues that complicate immunity:

1. Natural immunity (from a prior infection) is at least as good as a full COVID-19 vaccination, as both sources provide at least short-term protection. Although antibody levels drop off after a few months, the concentrations level off at roughly 10-20% of maximum concentration. Memory B cell concentration from infection remains the same at 12 months post-infection. Memory B cells quickly trigger a secondary immune response after recognizing a specific pathogenic antigen. Reinfections, although rare – are occurring.

2. Adding a COVID-19 vaccine to patients who had a prior infection boosts COVID-19 antibody levels 50x greater than before vaccination. “How long will this immunity last?” is the question we don’t know the answer to yet. Breakthrough infections are already occurring. A July super spreader event in Massachusetts (an indoor and outdoor event where people were in very close proximity) is the reason the CDC is recommending masks again. Breakthrough cases are happening, and lowering one’s “viral load” (via less exposure) will prevent disease, or at least lessen severity.

3. Viral Load. In May of 2020, the Fitzpatrick team published an evidence-based post describing viral load and how it impacts disease transmission. Masking and social distancing lower the chance of someone getting (or sending) enough viral particles to cause infection. Our team believes that viral load may be the most important variable for understanding how breakthrough cases and reinfections are occurring.

4. Boosters. Although we were not so sure about boosters in our May, 2021 post “Will We Need COVID-19 Boosters?”, it now seems inevitable – whether one has had natural infection and/or has already been vaccinated. Vaccines can boost the body’s immune response, even for those who had a prior infection.

5. Children. Emergency Use Authorization for children <12 has not yet been granted. Compared with adults, children are more commonly asymptomatic or have mild symptoms, yet children have been seen as a significant source of transmission.

6. People who are immunocompromised. The elderly and those with compromised immune systems are at a high-risk for a severe COVID-19 Delta variant infection (severe respiratory disease and death), even if they already have some immunity. Please be considerate of them.

7. Vaccine-hesitancy and antivaxxers. The CDC reported that 99.9% of those fully vaccinated will NOT experience a severe COVID-19 infection. Conversely, since the Delta variant is twice as contagious as earlier variants, we are witnessing massive COVID-19 spread among the states/communities that have high unvaccinated rates. Over 80% of current COVID-19 pandemic cases are in USA counties with <40% vaccination rates. Complicating matters, there are large numbers of healthcare workers who ardently oppose COVID-19 vaccinations. As expected, COVID-19 vaccination rates closely correlate with education level:

• Physicians: 96% COVID-19 vaccination rate


• Nurses: <50%


• Aides: lower rates than nurses

8. The Delta variant is twice as transmittable than earlier COVID-19 variants. It is a LOT easier to catch.