COVID: Note on Vaccines and Reinfections

Published on August 14, 2020

News overnight that the UK has broadened its quarantine requirements for travelers from European countries with spiking COVID cases is a stark reminder of the ongoing challenges faced by policymakers as they seek to re-start social and economic activity.

Juxtaposed with that is the continued advance in vaccine research and development that included a rather unusual unveiling earlier this week by the Kremlin of an allegedly successful, first to market, “Sputnik V” vaccine.

That led us to check in again after a long pause with our outside epidemiology expert Dr. Sarah Zaidi for her general thoughts on the progress of vaccine development, as well as on anecdotal reports of more cases of reinfection in individuals who had already contracted and recovered from the disease.

We share her brief comments with you below.  As a reminder, these are the views solely of Dr. Zaidi, generously simplified for us to layman level, and are not produced by SGH research.

“Both the China and Russian vaccines are of the adenovirus type that is being developed by the Oxford/AstraZeneca consortium. Not surprising, very limited data has been shared by the Chinese and Russians, but phase 2 trial data from Oxford shows pretty good effectiveness (>98%) with one dose of boosting T-cell response.

“The open question remains whether these vaccines will confer long term immunity or like the flu vaccine will need to be given periodically. The safety issues in elderly and patients with chronic diseases is also unknown.

“The Oxford vaccine in its phase 3 clinical trials will include the 60+ [demographic], but thus far most testing has been done in healthy 18 to 55 years old. The Pfizer vaccine is also showing great promise; another mRNA vaccine like Moderna. My best guess is that there will be a vaccine or vaccines in production by early next year, and it will be perceived as a game changer.

[Regarding Reactivations]

“The reactivation of the virus in some [cases] is probably linked to our immune functions.

“The virus latches onto ACE2 receptors, which are in many systems of our body, and probably triggers a response if our adaptive immune system doesn’t recognize it as an earlier infection. Perhaps, there are subtle mutations of the virus.

“I haven’t fully followed up the reactivation cases, but since they are usually amongst the elderly it probably means that the immune system is having “memory issues.”

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