The title above is one of several great turns of phrase in the book I just finished reading, Edith Wharton's Age of Innocence. It refers to an episode where the protagonist was at a loss for words during a poignant encounter and presumably only later thought of something better to have said. I've been there.
Next Round for Covid Vaccine
The FDA's Vaccine and Related Biological Products Advisory Committee finally had their meeting last week; it had been postponed to give a little more time to see which way the new SARS-CoV-2 variants were headed. I was able to listen in on most of the meeting and have reviewed all the documents. The vote was unanimous to choose a monovalent JN.1-based vaccine for the next iteration, no surprise and in agreement with the recent WHO decision I discussed recently. (For those interested, there is quite a bit of international collaboration on these types of decisions. See the ICMRA posting about covid vaccines.) Still, there were some interesting updates on covid in general. I'll try to distill this down into the main takeaways.
The Latest on Epidemiology (from Thornburg FDA presentation)
Current circulation of SARS-CoV-2 is relatively low. Although our reporting is not as reliable these days, looking just at percentage of positive covid tests in orange you can see we are in a lull now, though perhaps with a hint of an uptick. This is pretty similar to last summer when we saw a bit of a surge in summer into fall and winter. SARS-CoV-2 still has not come around to a winter seasonality seen with other coronaviruses of with influenza, making predictions for surges and vaccine composition very tough.
JN.1 lineages replaced XBB.1.5 lineages during winter 2023-2024. I like the depiction below because it's looking at normalized numbers of positive tests rather than a percentage of positive tests due to different variants. This gives a better appreciation of numbers of cases and shows that we are still talking about relatively low numbers compared to 2022.
Here's a closeup of the most recent part of the above slide showing that KP.2-like, KP.3, and other JN.1 derivatives are starting to take over, though still all at very low numbers.
The recent subvariants have very few differences from other JN.1-derived strains and antigenically are very similar. This has important meaning for vaccine choice - should it be the original JN.1 variant or one of these newer KP.2 or KP.3 type subvariants, currently at extremely low numbers? Look at the last 2 rows in the table below, showing that these newer subvariants have very few mutation differences from the earlier JN.1-like variants.
In a totally new and as yet unpublished CDC analysis, severity of JN.1 infections does not appear to be worse than earlier lineages. The trend was towards milder illness, though not statistically significantly different. Note these numbers are just for adults.
Vaccine Effectiveness in Children (from Link-Gelles FDA presentation)
This it tough to estimate because children generally have milder disease, plus so few children are vaccinated. Adult data is pretty favorable for VE; SGT failure is a faster method of testing and correlates will with JN.1 lineage strains. 2023-2024 VE drops a little with these strains compared to effectiveness against XBB lineage strains.
On the pediatric side, it's important to remember that the vast majority of US children have been infected with SARS-CoV-2 at some time in their lives - this has been apparent since late 2022.
So, it's important to determine any VE now in light of prior infection and vaccination. We can't rely on older estimates. Here's the best and latest estimates for VE in children who received vaccine in the past year. Confidence intervals are relatively wide, reflecting the small numbers able to be studied, but do show benefit in prevention of ED or urgent care use. VE wanes with time after vaccination as it does with all age groups, but there is clear benefit for covid vaccination of children.
David Wentworth, representing WHO, delivered a wonderful explanation of the complexities in choosing among current subvariants for vaccine inclusion. He had this great quote: "... antigenic evolution just speeds up waning immunity." The variant evolution we're seeing now is parallel, i.e. lots of different subvariants evolving on their own, in parallel, rather than one subvariant evolving into another, and then into another, etc. Parallel evolution is what XBB lineages did previously, and we're seeing it now in the JN.1 groups. The slide below demonstrates this process with a timeline on the X axis.
The dilemma in choosing composition of the next vaccine is that no one knows which way the very new subvariants will evolve in terms of antigenic similarity to earlier JN.1 strains. Currently, KP.2, KP.3, and JN.1.23 are within what is thought to be close proximity to JN.1 in terms of antigenic similarity and therefore a vaccine based on any of those likely will have cross-reactivity with one another, enough to provide protection. However, as illustrated by the arrows, it just isn't known how the offspring of the newer subvariants will evolve - will it be farther away from JN.1 and each other, or will it remain relatively stable?
No one can predict what next fall's or winter's subvariants will look like. Once they appear, new lab testing would need to be done, ideally using human serum containing antibody to the newer strains, which Wentworth stated would take about a month to produce. So, it's not something that can be turned around quickly.
Also, it bears mentioning that virtually all of the immunity studies involve neutralizing antibody. Antibody does correlate well with VE, but T-cell immunity also is important. We don't see as much data about this arm of the immune system because the studies are more difficult.
All 3 US vaccine manufacturers, Moderna, Pfizer, and Novavax, presented their new data at the meeting. They are developing and testing new vaccines "at risk," meaning the companies are making vaccines without funding currently, risking their own research and development dollars, hoping whatever they are working on will be recommended for the next covid vaccine rounds and allow them to recoup their investment. Moderna and Pfizer have both developed JN.1- and KP.2-based mRNA vaccines. Novavax, the adjuvanted protein-based vaccine, only developed a JN.1-based vaccine. The protein vaccine takes much longer to construct than do mRNA vaccines, about 6 months to get good data in all. So, if a KP.2 or other vaccine were recommended, Novavax would need to start over and wouldn't be ready until about December.
I don't usually like to use pharma slides to illustrate points, but this one from Pfizer isn't biased in favor of their product and I think nicely shows the current situation, including how closely related the newer subvariants are to JN.1.
In the discussion after the vote to have a monovalent JN.1-based vaccine, which could mean one based on KP.2, the majority of the group felt that using the JN.1 variant rather than KP.2 or another subvariant was the best route, both to allow Novavax to be ready this fall but also not to take a chance that fall and winter predominant subvariants might be more antigenically removed from KP.2 antigenically. All in all I felt this was the right choice, though I probably wouldn't have let Novavax's problems affect the decision; very few US residents have received Novavax in the past, though it is nice to have an alternative to mRNA vaccines available.
On June 7 the FDA formally recommended sticking with the JN.1 strain for this next vaccine round. Next step with be the CDC's Advisory Council on Immunization Practices meeting the end of this month, where the official seal of approval will be issued. I'm sure Moderna, Pfizer, and Novavax already are ramping up production.
NASEM Long Covid Report Available
Long covid remains a quagmire, lots of different symptoms, many of which are vague, and still no definite light shed on diagnosis and treatment of what is likely a heterogenous group of conditions requiring different approaches. The National Academies of Science, Engineering, and Medicine published their full report, available free online. I haven't gotten through all of it, it's pretty long, but it is of interest to those practitioners who see these patients. Most of the evidence is from adults, but it appears that pediatric patients tend to have a better prognosis, especially if improvements are occurring in the first year after onset. Note that a positive covid test is not required for diagnosis testing may not have been done at the time of the triggering infection and antigen or PCR tests will have reverted to negative by the time a long covid diagnosis is considered.
Doxycycline for Post-Exposure Prophylaxis of STIs
The official guidelines appeared this past week, although the gist of the recommendations had been floated previously. Particularly high risk groups are gay, bisexual, and other men who have sex with men and transgender women. The summary is very helpful for practitioners who may want to print out and post Box 1 and Box 2 in their workspaces. Note that the recommendations apply just to those high risk groups.
Summer Bugs!
Bugs in the sense of both insects and microbes. We now have more details about a new rickettsial agent, termed species C6269, that caused a Rocky Mountain Spotted Fever-like illness in 2 individuals in northern California last summer. Both had severe disease, were hospitalized and treated with doxycycline, and survived. As always, keep RMSF and other tick-borne diseases in mind during our warm months.
Speaking of bugs, our dog came down with a skin abscess, expertly debrided by her veterinarian. She is now enjoying chewable amoxicillin/clavulanate but is less thrilled with her "cone of shame." The vet had another bug concern, however. She didn't want the dog to spend much time outside - apparently it is also maggot season, and they love open dog wounds. The vet doesn't know I'm an ID doctor, and I was trying to come up with some clever comment on maggots but failed at that moment - belated eloquence of the inarticulate!
Courtesy of Wikipedia. Hope you aren't eating as you read this.