reproductive number – Pediatric Infection Connection

Optimistic Omens?

Bud WiedermannApril 3, 2022Leave a comment

It's becoming a little tougher to rely on pandemic data now. Reporting from most, if not all, US jurisdictions is infrequent plus misses most of the home test results; we know individuals generally aren't going to report their home rapid test results. Furthermore, testing around the globe is likely worse, driven additionally by lack of testing resources.

So, to satisfy my craving for data I've had to turn to a bit of a jigsaw puzzle strategy to assemble data pieces into a big picture.

Friends Across the Pond, Plus Some CDC Data

Europe, though with different pandemic epidemiologic drivers, has helped to foreshadow events in the US. I turned to England's poop patrol first. The image below is one of many from the UK's excellent reporting system; focus on the blue line depicting England's viral concentration in wastewater through early March.

What you see are viral levels, mostly representing the BA.2 omicron subvariant, coming down to what was seen at the low point last October. I find this particularly encouraging because this downtrend is happening without British healthcare system overload. Furthermore, R value (reproductive number) in the UK also is heading down. (This last link is only for hardcore pandemic geeks, at the website you then need to download a spreadsheet and study the data.)

In the US, it's hard to find much about the pandemic in the lay press, probably a combination of other important news, less data, and overall pandemic fatigue. The screenshot below is from the CDC's variant tracker; note the striking and rapid appearance of BA.2.

Again, what is a hopeful sign is that we have seen BA.2 virtually take over most of the country, but without a rapid rise in healthcare resource strain. The fully assembled puzzle may be showing us that while BA.2 rapidly became the predominant strain, it did not result in a major illness surge. The next few weeks in the US will reveal a clearer picture.

But Wait, There's More

I was super-excited to see the FDA's new industry guidance for COVID-19 vaccination, the first update in about a year. Other than the vaccine industry, I may be the only other person to be thrilled to see this guidance. The press and even most of my healthcare alerts seem to have ignored it. It's pretty dense, boring reading, but the meat is in Appendix 2 on page 21 where the approach to vaccines for new variants is discussed. Although the FDA always has a disclaimer that these are all nonbinding recommendations, you can bet Pfizer, Moderna, and the other vaccine players will be paying close attention to this roadmap for future trials, likely later this year.

I deliberately chose the term "omen" at the top of this post, feeling like I may as well be reading tea leaves or using similar methods to divine the future. Nonetheless, my puzzle work today reminds me to look forward to my summer vacation with our 1000-piece jigsaw puzzle, this one with a bunch of trees that all look alike. If our plans stay intact, we'll have (and need) the whole family working on this one.

Happy Vernal Equinox!

Bud WiedermannMarch 20, 2022Leave a comment

Yes, the first official day of spring is today, Sunday, March 20. To be more precise it occurs at 11:33 AM EDT. (Note, after reading last Sunday's Washington Post comics section, I realized I erroneously referred to EDT as Daylight Savings Time, rather than Daylight Saving Time, in last week's posting.) While we await further results for COVID-19 vaccine trials in younger children as well as possible EUAs for 4th doses of vaccine for adults, let's see what else spring has to offer.

COVID-19 Hospitalization Rates in 0 - 4 yo Children

CDC released new data on March 15 confirming what everyone working in a children's hospital already knew: the omicron surge was bad news for young children, even though overall the variant did not appear to be more virulent than its predecessors. Hospitalization rates were higher in young children than at any time during the pandemic. One picture says it all.

Meanwhile, I remain focused on Europe as a possible harbinger of things to come for the US. Certainly as COVID-19 restrictions relax across the world we can expect an uptick in cases, but the real question I have is whether the uptick now in Europe is simply that or represents another surge due to the BA.2 subvariant. I am closely following my daily reports from uk.gov and have noticed a drifting up of the weekly reproductive number. At the last update a few days ago, the R value is estimated at 1.1-1.4. As explained in their helpful report, " An R value of 1 means that on average every person who is infected will infect 1 other person, meaning the total number of infections is stable. If R is 2, on average, each infected person infects 2 more people. If R is 0.5 then on average for each 2 infected people, there will be only 1 new infection. If R is greater than 1 the epidemic is growing, if R is less than 1 the epidemic is shrinking. The higher R is above 1, the more people 1 infected person infects and so the faster the epidemic grows." Note this week's number really represents transmission that happened 2-3 weeks ago, it takes time for reporting and tracking to be reflected in R values. In my opinion, this currently reported R rate is consistent with just relaxing of restrictions, but if it goes much higher it probably means we're headed for a more significant surge that might call for going back to masking and other nonpharmaceutical interventions.

Remember Tickborne Diseases?

Yes, it's hard to think about anything but COVID sometimes, but spring also brings us into tick season. (Note that climate change increasingly allows for tick survival throughout the year, but there will be more of them around now, for the next several months.) In the DC area of course we need to continue to be on the watch for Lyme disease; providers should make use of excellent guidelines for management.

Recently another tickborne disease appeared in the news as Heartland virus, aka HRTV, was detected in lone star ticks (Amblyomma americanum) in Georgia. HRTV is still rare, only about 40 cases reported in the US since first described in 2009, but it is serious. Clinically it is a hemorrhagic fever with thrombocytopenia syndrome with a high fatality rate, though the rate is probably falsely elevated a little bit because milder cases would not have resulted in detailed investigation for causes.

While we are on the subject, keep in mind Bourbon virus, named for the county in Kansas where it was first discovered in 2014. It isn't as severe as HRTV and has not been reported in the DC area.

Remember to advise your patients and their families about prevention and management of tick bites. However, don't let this keep anyone from enjoying the outdoors!

Roller Coaster Week

Bud WiedermannFebruary 13, 2022Leave a comment

I guess we all should be accustomed to the ups and downs of the pandemic. We continue to see good news with waning of the omicron surge around the world, but parents of children under 5 had a bit of a jolt on Friday with the news that the Pfizer vaccine will not be discussed by the FDA next week as originally planned. We now await ongoing data from the trial which has begun a booster dosing phase. Regular readers of Pediatric Infection Connection will know that I oversee this trial at Children's National Hospital, but I have no knowledge of the data submitted by Pfizer to the FDA so can't provide any independent opinion.

Booster News?

Speaking of boosters, CDC released some important new information about boosters, some of which pertains to children. First, an early release in MMWR highlighted waning of effectiveness of 2- and 3-dose mRNA vaccines. This is sort of a glass half empty or full view, I was actually more encouraged by the continuing effectiveness, particularly for boosted individuals, against severe disease and hospitalization. Just looking specifically at the data from the omicron-dominant time period, vaccine efficacy (VE) in preventing emergency or urgent care visits was 87% 2 months following a third or booster dose though dropped to 66% beyond 5 months (note few data available for this latter estimate). VE in preventing hospitalization was 91% and 78% for those 2 intervals post third dose. This is by no means the final word, lots of limitations in this study and also it looked only at individuals 18 years of age and older and did include a significant number of people with immunocompromise and other risk factors for severe COVID-19 disease. No information about how these risk factors specifically affected VE.

Also, as promised the CDC issued an update to guidance for vaccination of those with moderate or severe immunocompromise to include a fourth dose in some circumstances. This update applies to people down to 12 years of age and provides a good road map for vaccination of those individuals.

Variant Viewing

I'd definitely be happier stargazing or watching butterflies and bees in season, but lately I've been keeping an eye on the BA.2 subvariant of omicron. It has started to appear in our CDC data (after clicking on this link, choose Variants and Genomic Surveillance, then Variant Proportions from the left-side menu). BA.2 now comprises 3.6% of isolates as of Feb 5 compared to 96.4% omicron BA.1) and similarly has increased slightly in the UK. As I indicated last week, it is more transmissible than the original omicron variant, but it isn't clear whether prior infection with omicron BA.1 confers some immunity against BA.2. That is probably the key factor in determining if we will see another surge due to BA.2.

I also note some encouraging news in the UK that the reproductive number is now estimated at 0.8 to 1.0, a milestone that signals flattening or decrease in the pandemic. Of course it could be just another ride on the roller coaster but I choose to take this as a further good sign.

Tag: reproductive number