Tag Archives: vaccine

New EAST Practice Guideline: Spleen Vaccines After Angioembolization

I am trying to figure out how I missed it! The Eastern Association for the Surgery of Trauma (EAST) snuck a new practice management guideline into the Injury journal last fall. And it desperately tries to answer a question that has been hanging around for several years. Do we vaccinate spleen injury patients who undergo angioembolization or not?

I’ve been pondering this for some time and have reached my own conclusion based on some very old literature. Decades ago, we figured out that removing the spleen significantly affects immune function. Splenectomy patients are known to be more susceptible to encapsulated bacteria like Neisseria meningiditis, Streptococcus pneumoniae, and Haemophilus influenzae. Most trauma centers routinely vaccinate these patients before they are discharged home.

With the more recent emphasis on splenic salvage and nonoperative management of injury to this organ, angioembolization has become commonplace. This technique can be done in two ways: proximal and distal. Proximal embolization blocks the splenic artery, so there is no further blood flow to the spleen through it. Distal embolization (selective or super-selective) strives to block flow to very specific areas of the organ.

Do we need to give the vaccines if we cut off blood flow to pieces of the spleen or the main splenic artery? Based on my appreciation of very old splenectomy and partial splenectomy papers, it looked like we should in some cases. One report showed that splenic protection from encapsulated bacteria required about 50% of the spleen to be present and perfused by the splenic artery. This caveat stems from a time when we would perform a trauma splenectomy, dice the spleen up on the back table, and then implant a bunch of spleen cubes into the mesentery to try to provide some immune protection. Turns out that the pieces lived but didn’t do a damn thing.

My practice, then, has been to look at the fluoro images and estimate how much of the spleen was left. I would order the vaccines if a main splenic artery embolization (proximal) was performed. If a distal embolization were performed, I would eyeball the amount of devascularized spleen and give the vaccines if it looked like more than half was dark. Not very precise, I know.

But what would EAST say? They tried to perform a systematic review and meta-analysis of studies that compared outcomes in splenectomy vs. angioembolization patients. Unfortunately, there isn’t a lot of research material out there. So they settled on looking at papers that analyzed immune function, typically using B-cells, T-cells, and antibodies. The authors performed two comparisons: angioembolization vs. splenectomy and angioembolization vs. control.

Angioembolization vs. Splenectomy

These papers compared embolization patients who may or may not have spleen function to splenectomy patients who definitely have none. Embolization patients had fewer infectious complications during their hospital stay and better immune function using the indirect methods noted above. Unfortunately, the data quality was poor, with a significant risk of bias. There was no stratification of proximal vs. distal embolization. Nevertheless, this suggests that, at least overall, the embolization patients retained immune function.

Angioembolization vs. Controls

What about comparing embolization patients to spleen-injured patients who did not undergo any procedure? They should have normal function. Again, the quality of the very few papers available was low. But overall, there was no difference in immune function between the groups.

Bottom line: The EAST review team conditionally recommended against routine spleen vaccines after angioembolization for spleen injury. They concluded that immune function was maintained, so it should not be necessary.

What, you ask, about patients with proximal splenic embolization? The reality is that this only stops inflow from the splenic artery, and only for a few days or weeks. It may slowly resume over time. And it does nothing to the inflow from the short gastric arteries. Apparently, this is enough to provide immune protection against infection.

Whether this is actually true is open to debate. We have no idea if the numbers of T- and B-cells seen and the antibody titers are actually enough to avoid overwhelming post-splenectomy sepsis. And unfortunately, this condition is so rare that we will never accumulate enough cases to make a definitive statement.

But for now, it is probably okay to forgo the vaccines in patients undergoing angioembolization. Besides, the differing guidelines on which vaccines to use, when to give them, and when to schedule boosters were getting way out of hand! Please keep it simple!

Reference: Vaccination after spleen embolization: a practice management guideline from the Eastern Association for the Surgery of Trauma. Injury 53:3569-3574, 2022.

Spleen Vaccines: So Confusing! – Part 2

Who needs to get these vaccines? Obviously if your patient’s spleen was surgically removed, they should get it. But what about patients who underwent angioembolization? Unfortunately, the only data available is either very old or is based on antibody response to the vaccine. And antibody titers do not predict immunity to infection, so these studies are close to meaningless.

Old research showed that the spleen’s immune function was preserved as long as 50% of its blood flow was delivered through the splenic artery. How can you tell if half of the spleen is still functioning after splenic angioembolization? Look at the images and make an educated guess. If in doubt, vaccinate.

When is the best time to vaccinate? There has been much gnashing of teeth regarding early vs late vaccination. The arguments against early vaccination center around the typical immune suppression seen with major trauma. However, trauma patients frequently do not appear for all their followup visits and would not receive vaccines at all if they are a no-show. So I recommend vaccinating as early as possible during the hospital stay to avoid forgetting. The data recommending waiting until just before discharge are also based on antibody titers, and I don’t buy it.

Bottom line: I’m not an epidemiologist. But making a set of vaccination rules more complicated for a complex population seems unwise. Especially since the added vaccine offers protection for only one more serotype of Pneumococcus.

But I can’t argue with the FDA and CDC. I have no idea of the wheeling and dealing that occurred to get the new vaccine approved. All we can do is follow the recommendations the best we can, and try to remind our patients to get that Pneumovax and meningococcal conjugate booster five years down the road. Good luck with that.

Spleen Vaccines: So Confusing! – Part 1

Earlier this year, there were a lot of television commercials for Prevnar 13, a 13-valent pneumococcal vaccine for immun-ocompromised or asplenic adults. And interestingly, I noticed that the CDC has added a recommendation that these patients receive this vaccination, followed by the original 23-valent vaccine (Pneumovax 23) 8 weeks later.

WTF? Patients with splenectomy (or significant angio-embolization) for trauma are considered functionally asplenic. And although the data for immunization in this group is weak, giving triple vaccinations with pneumcoccal, H. flu, and meningococcal vaccines has become a standard of care.

This was difficult enough already because there was debate around the best time to administer: during the hospital stay or several weeks later after the immune system depression from trauma had resolved. The unfortunate truth is that many trauma patients never come back for followup, and so don’t get any vaccines if they are not given during the hospital stay.

And then came the recommendation a few years ago to give a 5-year booster for the pneumococcal vaccine. I have a hard time remembering when my last tetanus vaccine was to schedule my own booster. How can I expect my trauma patients to remember and come back for their pneumococcal vaccine booster?

So what do we do with the CDC Prevnar 13 recommendation? If we add it, it means that we give Prevnar while the patient is in the hospital, and then hope they come back 8 weeks later for their Pneumovax. And then 5 years later for the booster dose. Huh?

Looking at the package insert, I read that Pneumovax 23 protects against 23 serotypes of S. Pneumo, which represent 85% of most commonly encountered strains out there. So it’s not perfect. Prevnar 13 protects against 13 serotypes, and there is no in-dication as to what percent of strains encountered are protected against.

So I decided to dig deeper and look at the serotypes included in each vaccine. They are shown in the chart below. The 23 bars with maroon in them (solid or striped) are Pneumococcal serotypes covered by Pneumovax 23. The 13 bars containing gray are ones covered by Prevnar 13. There is only one serotype in Prevnar 13 not covered by Pneumovax 23, serotype 6A. Unfortunately, it’s nearly impossible to find the prevalence of infections by serotype, and it varies geographically and over time anyway. So does cover-age of a single extra serotype by Prevnar 13 justify an additional vaccination and complicated administration schedule? Hmm.

It turns out that there is one significant difference between these two vaccines. Pneumovax 23 is a polysaccharide vaccine made up of fragments of polysaccharide from pneumococcus cell walls. Prevnar 13 is a “conjugated vaccine,” meaning that the polysaccharides are linked to a protein. This is thought to increase the immune system response to the vaccine.

(click for full-size graph)

The current CDC recommendations are listed below. In the old days, we just gave three vaccines before the patient left the hospital. Then the Pneumovax 23 booster was added at 5 years. Same for the meningococcal serogroup B booster at 4 weeks. Then the meningococcal conjugate vaccine (Menactra) came along and was added (with a booster at 8 weeks). Finally, Prevnar 13 was added with its own booster, and Pneumovax 23 was delayed for 8 weeks. Oh, and don’t forget the 5 year boosters for both Pneumovax 23 and the meningococcal conjugate vaccines. It has become very complicated.

(click for full-size chart)

In my next post, I’ll try to make sense of this mish-mash and offer some thoughts on how to decide what to do for your patients.

Prevnar 13 And Spleen Trauma

Recently, I’ve noticed television commercials for Prevnar-13, a 13-valent pneumococcal vaccine for immunocompromised or asplenic adults. And interestingly, I noticed that the CDC has now added a recommendation such that these patients receive this vaccination, and then the good old 23-valent vaccine (Pneumovax) 8 weeks later.

WTF? Patients with splenectomy (or significant angio-embolization) for trauma are considered functionally asplenic. And although the data for immunization in this group is weak, giving triple vaccinations with pneumcoccal, H. flu, and meningococcal vaccines has become a standard of care.

This was difficult enough already because there was debate around the best time to administer: during the hospital stay or several weeks later after the immune system depression from trauma had resolved. The unfortunate truth is that many trauma patients never come back for followup, and so don’t get any vaccines if they are not given during the hospital stay.

And then came the recommendation a few years ago to give a 5-year booster for the pneumococcal vaccine. I have a hard time remembering when my last tetanus vaccine was to schedule my own booster. How can I expect my trauma patients to remember and come back for their pneumococcal vaccine booster?

So what do we do with the CDC Prevnar-13 recommendation? If we add it, it means that we give Prevnar while the patient is in the hospital, and then hope they come back 8 weeks later for their Pneumovax. And then 5 years later for the booster dose. Huh?

Looking at the package insert, I read that Pneumovax protects against 23 serotypes of S. Pneumo, which represent 85% of most commonly encountered strains out there. So it’s not perfect. Prevnar-13 protects against 13 serotypes, and there is no indication as to what percent of strains encountered are protected against.

So I decided to dig deeper and look at the serotypes included in each vaccine. Here they are:

  • Pneumovax: 1, 2, 3, 4, 5, 6B, 7F, 8, 9N, 9V, 10A, 11A, 12F, 14, 15B, 17F, 18C, 19F, 19A, 20, 22F, 23F, and 33F
  • Prevnar: 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F

I bolded the serotypes in Prevnar-13 not found in the Pneumovax vaccine. There was only one, serotype 6A. Unfortunately, it’s nearly impossible to find the prevalence by serotype, and it varies geographically and over time.

Bottom line: I’m not an epidemiologist. But making a set of vaccination rules more complicated for a complex population, and for indications that are a bit weak in the first place, seems unwise. Especially since the added vaccine offers protection for only one more serotype of Pneumococcus.

So please help me out here. Show me something I’m missing. Otherwise, I’ll stick to the original three vaccines, and try to remind my patients to get that booster five years down the road.

Related posts:

Reference: Use of 13-Valent Pneumococcal Conjugate Vaccine and 23-Valent Pneumococcal Polysaccharide Vaccine for Adults with Immunocompromising Conditions: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 61(40):816-819, October 12, 2012.

EAST 2017 #12: Revaccination Compliance After Splenectomy

The incidence of overwhelming post-splenectomy sepsis, and the need and effectiveness for vaccination after splenectomy is still subject to debate. However, the administration of three vaccines to protect against encapsulated bacteria is a standard of care. For decades, this was a one time thing and the vaccines were usually given before the spelenctomized trauma patient was discharged from the hospital.

Then several years ago, the CDC updated their recommendations to include a booster dose of 23-valent penumococcal vaccine. Trauma professionals have inconsistently advised their patients about this dose, and patients have not reliably sought their booster.

Researchers at Christiana Care in Delaware looked at this potential problem by identifying all of their trauma splenectomy patients over a 10 year period. They were interviewed by phone to determine their understanding of the asplenic state and the need for booster vaccination.

Here are the factoids:

  • During the 10 year period, 267 trauma splenectomies were performed
  • 196 survived, but only 52 agreed to participate (? – see below)
  • Although all patients received vaccines before discharge (!), only 23% were aware that they had
  • Only about half of patients were aware that they may be at risk for infectious complications
  • Only 19% understood they would require a booster dose, and 22% had actually received one (?? – see below)

Bottom line: Although we still aren’t sure how important these vaccines are, vaccination is the standard of care. This study, although a little confusing, shows that we are falling down in educating our patients about the impact of their splenectomy (surgical or via embolization). And it’s difficult for anyone to remember to get a booster shot. Are you up to date on your tetanus vaccination?

This abstract shows us that we need to counsel these patients prior to discharge regarding their at-risk condition. We also need to make sure they (and their primary care provider) are aware that they need to get a pneumococcal booster five years down the road.

News flash! Take a look at page 3 of the CDC recommendations (download here) to see the official recommendations regarding pneumococcal vaccination. It is recommended that PCV-13 vaccine (Prevnar 13) be given first, then the 23-valent vaccine (Pneumovax) 8 weeks later! This complicates things a bit, since both pneumococcal vaccines cannot be given while the patient is still in the hospital. This will reduce the likelihood that patients will get their second pneumococcal vaccine.

Questions and comments for the authors/presenters:

  1. The number of patients is off by one. There were 267 splenectomy patients, 49 died in the hospital and 23 after discharge. 267-49-23=195, not 196.
  2. Only 52 of this 195 agreed to participate. You were able to find all 195? It seems that some of these 143 patients just could not be located.
  3. Please clarify the numbers in my last bullet point. Of the 52 patients, only 9 were aware of the revaccination requirement, and only 1 got it?
  4. This is important work. What have you done to improve these numbers at your hospital?

Click here to go the the EAST 2017 page to see comments on other abstracts.

Related posts:

Reference: Revaccination compliance after trauma splenectomy: a call for improvement. Poster #31, EAST 2017.