▶️ Extensive discussions about potential protection from #monkeypox from pre-1980 smallpox (vaccinia) vaccinations.
▶️ What do we actually know, and
▶️ how well do we know it?
a thread.
1/n
Four main issues:
A. How long did vaccines protect against smallpox?
B. How often was/is 𝙧𝙚𝙫𝙖𝙘𝙘𝙞𝙣𝙖𝙩𝙞𝙤𝙣 recommended?
C. How common were smallpox infections after 𝙧𝙚𝙫𝙖𝙘𝙘𝙞𝙣𝙖𝙩𝙞𝙤𝙣 ?
D. How well does smallpox vax protect against #monkeypox?
2/n
A. Length of protection
▶️ From current ACIP guide, no definitive evidence, but epi studies suggest strong protection for <5 years, with some protection out to 10+ years.
3/n
B. Revaccination
1965 guidance says 5-year intervals are necessary based on epi data.
pubmed.ncbi.nlm.nih.gov/5897320/
4/n
B. Revaccination
▶️▶️ Current guidelines, 3-year intervals, especially if working with replicating/virulent orthopoxviruses, including #monkeypox.
(note: these are 𝙫𝙚𝙧𝙮 conservative for safety)
5/n
B. revaccination
How long do titres remain high, and what levels confer protection from infection?
Long-term followup, 🇮🇱 military.
▶️ "The protective significance of the above titre is unknown."
▶️ Primary + two-revacciantions "probably" sufficient
pubmed.ncbi.nlm.nih.gov/2155973/
6/n
B. Revaccination
Another study looking at measureable antibodies found quite different results from 🇮🇱.
ncbi.nlm.nih.gov/pmc/articles/P…
but ▶️ "The level of antibody required for protection against vaccinia is unknown also."
Likely a healthy cohort bias
ncbi.nlm.nih.gov/pmc/articles/P…
7/n
C. Infections after vax or revaccination
▶️ How common/severe were cases after vaccination?
Cases imported into Europe '50-'71 were reviewed, & most were revaccinated.
▶️Of secondary cases (local transmission), vast majority were vaccinated (61%, 412/680).
+ fatalities!
8/n
D. How well does smallpox vaccination protect against #monkeypox ?
JYNNEOS approvals were based on animal models and serological correlates.
cdc.gov/mmwr/volumes/7…
9/n
D. How well does smallpox vaccination protect against #monkeypox ?
WHO research roundtable states emphatically there are no clinical data to prioritize specific use-cases like post-exposure prophylaxis.
who.int/news/item/03-0…
10/n
▶️Where does all of this leave us?
1. We cannot assume any long-term #monkeypox protection from historical smallpox vaccination. It's likely limited.
2. While JYNNEOS may have good efficacy, we cannot assume it, and we have no data on 𝙚𝙛𝙛𝙚𝙘𝙩𝙞𝙫𝙚𝙣𝙚𝙨𝙨.
11/n
▶️▶️ What are next steps?
▶️ Plan for limited effectiveness against #monkeypox, and implement broader health programming
-----> there are no "magic bullets"
▶️ Uptake for post-exposure vax in UK was very low
▶️ Understanding this is essential!
eurosurveillance.org/content/10.280…
12/n
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