Covid Update: Boosting Boosters

The COVID-19 vaccines have proven to be highly protective against serious infection, hospitalization, or death among those who have been fully vaccinated. The most recent data suggest that protection against infection by the more transmissible Delta virus variant is lower than the Alpha strain that was common last winter. This means that fully vaccinated individuals can still become infected and transmit the virus even if they have no symptoms. Locally, over 92% of COVID-19 cases are among the unvaccinated, but rare cases do occur in vaccinated individuals (Del Mar has 209 reported cases, but the vaccination status of these individuals is not reported). This has led to a call for administering a third “booster” shot to those who may have poor or fading immune responses, including the immunocompromised (roughly 7% of the population) or older individuals who were first in line to get the vaccines early this year.


The immune response gets better each time it is stimulated with a virus or vaccine. A secondary or tertiary response takes advantage of an expanded number of “memory” cells that results in more potent antibody and cellular immunity. A third booster shot reawakens these memory cells and should result in an even more robust immune response. This means that the call for a COVID-19 vaccine booster shot makes sense from a basic immunology perspective.


The conclusion that vaccine efficacy is waning after 8 or more months is not as clear because of several confounding factors. The Delta variant is more transmissible and now accounts for the majority of COVID-19 infections. If the original protection studies had been performed when the Delta variant was prevalent, the level of protection might have been less than observed with the Alpha variant. The first vaccine recipients were older individuals who have poorer immune responses in general, so “waning” immunity might just mean weaker responses to the vaccines. Vaccinated individuals assumed (mostly correctly) that they were immune and probably resumed more risky behavior that led to greater exposure to the Delta variant.


So where does this leave us? The most important goal is to get everyone fully vaccinated as soon as possible. Getting a booster shot later in September makes sense if you had a weak response to the first vaccine shots or if you were first in line to get vaccinated. However, testing for protective immune responses is not readily accessible for most people, so you will have to depend on public health advisories rather than individual knowledge. A booster shot should provide a benefit and there is no downside (side effects should be similar to the second shot), so get ready to roll up your sleeves on more time.


(This is a rapidly evolving story—please check the Sandpiper website for updates.)