Case: 24-1372   Document: 37     Page: 1   Filed: 08/27/2025




   United States Court of Appeals
       for the Federal Circuit
                 ______________________

                  RONALD E. WHITE,
                   Petitioner-Appellant

                            v.

       SECRETARY OF HEALTH AND HUMAN
                   SERVICES,
               Respondent-Appellee
              ______________________

                       2024-1372
                 ______________________

     Appeal from the United States Court of Federal Claims
 in No. 1:20-vv-01319-TMD, Judge Thompson M. Dietz.
                  ______________________

                Decided: August 27, 2025
                 ______________________

     LISA A. ROQUEMORE, Law Offices of Lisa A. Roquemore,
 Rancho Santa Margarita, CA, argued for petitioner-appel-
 lant.

    ALEC SAXE, Torts Branch, Civil Division, United States
 Department of Justice, Washington, DC, argued for re-
 spondent-appellee. Also represented by C. SALVATORE
 D'ALESSIO, VORIS EDWARD JOHNSON, JR., HEATHER LYNN
 PEARLMAN, YAAKOV ROTH, DARRYL R. WISHARD.
                 ______________________

     Before LOURIE, REYNA, and STARK, Circuit Judges.
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 2                                               WHITE v. HHS




 LOURIE, Circuit Judge.
     Ronald E. White appeals from a decision of the United
 States Court of Federal Claims (“the Claims Court”) sus-
 taining a special master’s denial of his claim for compensa-
 tion under the National Childhood Vaccine Injury Act of
 1986, 42 U.S.C. §§ 300aa-1 et seq. (“the Vaccine Act”).
 White v. Sec’y of Health & Hum. Servs., 

 (2023) (“Claims Court Decision”); White v. Sec’y of Health
 & Hum. Servs., No. 20-1319V, 

 (Fed. Cl.
 June 2, 2023) (“Special Master Decision”). We affirm.
                        BACKGROUND
      White received a flu vaccine on November 1, 2017. Spe-
 cial Master Decision, at *1. Over a month later, on Decem-
 ber 5, 2017, he went to a clinic with a two-day history of
 dry cough, nasal congestion, runny nose, fatigue, and a fe-
 ver. 

 While there, a “nurse practitioner diagnosed him
 with a viral infection.” 

 Five days later, on December
 10, 2017, White went to the emergency department com-
 plaining of sudden generalized weakness that began ear-
 lier that day and ongoing upper respiratory symptoms that
 he reported had lasted ten days without improvement. Id.
 at *2. The attending physician suspected his generalized
 weakness was a symptom of Guillain-Barré Syndrome
 (“GBS”)—a neurologic condition in which the body’s im-
 mune system mistakenly attacks the peripheral nerves—
 while continuing to note that White was also likely still ex-
 periencing a viral illness. Id.
     That same day, White’s healthcare providers trans-
 ferred him to a different medical center and placed him in
 an intensive care unit (“ICU”) for “close monitoring of his
 respiratory status.” Id. While there, White’s providers
 continued to suspect that he had GBS “given his clinical
 presentation.” Id. And throughout his hospitalization
 “many of his treating physicians opined or speculated that
 his neurologic, GBS-like symptoms were associated with
 his preceding/ongoing respiratory infection.” Id.; see id. at
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 WHITE v. HHS                                                  3



 *8 (“[A]t least 14 treaters associated [White’s] upper res-
 piratory infection with the development of his GBS.”).
 Meanwhile, none of his providers “at this time proposed his
 more recent symptoms had anything to do with the flu vac-
 cine he had received almost six weeks before.” Id. at *2.
     Four days later, “on December 14, 2017, a sputum sam-
 ple from [White’s] lungs was taken and the culture of it re-
 vealed an H. influenzae infection,” i.e., a bacterial infection.
 Id. at *3 (footnote omitted). Consistent with that test re-
 sult, chest X-rays also showed worsening conditions in both
 lungs. Id. About a week later, on December 20, 2017,
 White’s doctors transferred him from the ICU to another
 unit to conduct further testing to rule out GBS mimics. Id.
 White’s providers “continued to repeat the hospital sum-
 mary that [he] likely had experienced H. influenza[e] pneu-
 monia” and upon discharge he was diagnosed with “GBS
 and H. influenzae pneumonia.” Id.
     On October 5, 2020, White sought compensation under
 the Vaccine Act by filing a petition at the Claims Court,
 which assigned his case to a special master. Id. at *1.
 White alleged that his GBS-related injury was caused by
 the flu vaccine that he received on November 1, 2017. Id.
 The special master determined that although White had
 established a prima facie case that the flu vaccine caused
 his alleged injury, id. at *15, he could not prevail because
 the government adequately showed that his unrelated
 H. influenzae infection was the “sole substantial factor”
 causing his GBS, see id. at *17–19. In so finding, the spe-
 cial master also explicitly eliminated the vaccine as a
 causal factor. See, e.g., id. at *18 n.16.
      White sought review of the special master’s decision in
 the Claims Court. See Claims Court Decision, 168 Fed. Cl.
 at 664. He argued there that the special master “erred by
 making arbitrary and capricious findings of fact and by
 failing to apply the correct burden of proof to the govern-
 ment.” Id. The Claims Court rejected his arguments and
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 4                                               WHITE v. HHS




 sustained the special master’s decision denying White en-
 titlement to compensation under the Vaccine Act. Id.
 White timely appealed, and we have jurisdiction under
 

(a)(3) and 42 U.S.C. § 300aa-12(f).
                         DISCUSSION
     White argues that there were at least two errors in the
 special master’s decision denying his petition for compen-
 sation. First, White argues that the special master’s deci-
 sion was not in accordance with the law because it failed to
 apply the appropriate legal standard. See Appellant
 Br. 19–23, 40–54. Specifically, he argues that the special
 master did not hold the government to its burden of prov-
 ing that a factor unrelated to the vaccine was the sole sub-
 stantial cause of his GBS-related injury. Id. If the special
 master had applied the correct legal standard, White con-
 tends, then the special master would have found that the
 evidence stands in “equipoise,” and that White is thus nec-
 essarily entitled to compensation. See id. at 37–40. Sec-
 ond, White argues that the special master’s findings under
 the first and third prongs of the Althen test were arbitrary
 and capricious. 1 See id. at 24–37; Althen v. Sec’y of Health
 & Hum. Servs., 

 (Fed. Cir. 2005). For
 the following reasons, we disagree.
                               I
     “In Vaccine Act cases, we review a ruling by the Court
 of Federal Claims de novo, applying the same standard
 that it applies in reviewing the decision of the special mas-
 ter.” Moberly ex rel. Moberly v. Sec’y of Health & Hum.


     1   White also argues that the special master’s finding
 under Althen prong two was flawed, but only to the extent
 that we agree with his arguments on Althen prongs one and
 three. See Appellant Br. 37. Because we affirm the special
 master’s findings under Althen prongs one and three, we
 need not address Althen prong two.
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 WHITE v. HHS                                               5



 Servs., 

 (Fed. Cir. 2010). As such, we
 review the special master’s factual findings under the “ar-
 bitrary and capricious standard,” and we review his legal
 rulings to determine whether they are “not in accordance
 with law.” Id.; Lampe v. Sec’y of Health & Hum. Servs.,
 

 (Fed. Cir. 2000). The “arbitrary and
 capricious [standard] is a highly deferential standard of re-
 view. If the special master has considered the relevant ev-
 idence of record, drawn plausible inferences and
 articulated a rational basis for the decision, reversible er-
 ror will be extremely difficult to demonstrate.” Hines ex
 rel. Sevier v. Sec’y of Dep’t of Health & Hum. Servs.,
 

 (Fed. Cir. 1991) (cleaned up).
      “The Vaccine Act distinguishes between so-called ‘Ta-
 ble injuries,’ for which causation is presumed when a des-
 ignated condition follows the administration of a
 designated vaccine within a designated period of time, see
 42 U.S.C. §§ 300aa-11(c), 300aa-14, and all other injuries
 alleged to be caused by a vaccine, known as ‘off-Table inju-
 ries,’ for which causation must be proved in each case.”
 Moberly, 

; de Bazan v. Sec’y of Health &
 Hum. Servs., 

 (Fed. Cir. 2008). Thus,
 for Table cases, the Vaccine Act “removes the petitioner’s
 difficult burden of proving actual causation by allowing the
 petitioner to rely on a table[-based] injury and a presump-
 tion of causation.” Knudsen ex rel. Knudsen v. Sec’y of Dep’t
 of Health & Hum. Servs., 

 (Fed. Cir. 1994).
 And if petitioners can overcome their initial burden of es-
 tablishing that presumption, “they are entitled to recover
 unless the government shows . . . by a preponderance of the
 evidence[] that the injury was in fact caused by factors un-
 related to the vaccine.” 

 (cleaned up); see 42 U.S.C.
 § 300aa-13(a)(1)(B).
     To prove actual causation for the factor unrelated to
 the vaccine, we apply the same standards that apply to a
 petitioner’s proof of actual causation in fact in off-Table
 cases. See Knudsen, 

 (“[T]he standards that
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 6                                                 WHITE v. HHS




 apply to a petitioner’s proof of actual causation in fact in
 off-[T]able cases should be the same as those that apply to
 the government’s proof of alternative actual causation in
 fact.”). Therefore, the government must
     show by preponderant evidence that the [factor un-
     related] brought about [petitioner’s] injury by
     providing: (1) a medical theory causally connecting
     the [factor unrelated] and the injury; (2) a logical
     sequence of cause and effect showing that the [fac-
     tor unrelated] was the reason for the injury; and
     (3) a showing of a proximate temporal relationship
     between [factor unrelated] and injury.
 Althen, 

. In addition to proving causation
 under Althen, the government must also establish that the
 factor unrelated is the agent “principally responsible for
 causing the petitioner’s illness, disability, injury, condition,
 or death.” 42 U.S.C. § 300aa-13(a)(2)(B) (emphasis added).
 We have described this “principally responsible for” lan-
 guage as a requirement that the government “present[] suf-
 ficient evidence to establish that [the factor unrelated] was
 the sole substantial factor in bringing about the injury.” de
 Bazan, 

 (emphasis added).
                                A
     White first argues that the special master legally erred
 by failing to hold the government to its burden of proof with
 respect to causation. See Appellant Br. 19–23. Relying on
 several off-Table cases, White contends that the govern-
 ment must eliminate the vaccine as causal if it is to show
 that the factor unrelated is more likely than not the sole
 substantial cause of the alleged injury. See id. at 22 (“[T]he
 government has the burden to prove that the covered vac-
 cine did not cause the harm.” (quoting Walther v. Sec’y of
 Health & Hum. Servs., 

 (Fed. Cir.
 2007))); id. at 21 (“[T]he government must eliminate the
 vaccine as a substantial contributing factor.” (citing
 Shyface v. Sec’y, Health & Hum. Servs., 

,
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 WHITE v. HHS                                                  7



 1353 (Fed. Cir. 1999))); 

 at 21–22 (“[T]he [government]
 must ‘exclude[ ] the vaccine as a substantial factor.’” (quot-
 ing de Bazan, 

)). By relying on off-Table
 cases, White treats his Table-based presumption of causa-
 tion the same as having established actual causation. See,
 e.g., Appellant Br. at 22 (“As the Federal Circuit pointed
 out in Walther, ‘the Petitioner generally has the burden on
 causation,[‘] (and in [White’s] case, as a Table case, it is
 presumed)[.]” (quoting 

)). But White mis-
 apprehends our case law and misapplies off-Table cases to
 the Table case at issue here.
      Off-Table cases are different from Table cases. In off-
 Table cases, the petitioner “is not afforded a presumption
 of causation and thus must prove causation-in-fact.” de Ba-
 zan, 

 (citation omitted). Causation-in-fact
 in the Vaccine Act context “is the same as ‘legal cause’ in
 the general torts context.” 

 (quoting Shyface, 

); see also Grant v. Sec’y of Dep’t of Health & Hum.
 Servs., 

, 1147 (Fed. Cir. 1992) (“The Table re-
 places traditional tort standards of causation in fact with a
 causation in law based on temporal association.”). Apply-
 ing tort law concepts, we have explained that “the vaccine
 is a cause-in[-]fact when it is a ‘substantial factor in bring-
 ing about the harm.’” Id. (quoting Restatement (Second) of
 Torts § 431); see Shyface, 

 (“We adopt the
 Restatement rule for purposes of determining vaccine in-
 jury, that an action is the ‘legal cause’ of harm if that action
 is a ‘substantial factor’ in bringing about the harm, and
 that the harm would not have occurred but for the action.”).
 Therefore, in off-Table cases “the petition must affirma-
 tively demonstrate that the injury or aggravation was
 caused by the vaccine.” Grant, 956 F.2d at 1147–48 (quot-
 ing H.R. Rep. No. 99-908, at 18 (1986), reprinted in 1986
 U.S.C.C.A.N. 6344, 6356, 

, at *15).
      In contrast, a petitioner in a Table case who meets his
 initial burden—alleging a designated condition following
 the administration of a designated vaccine within a
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 8                                               WHITE v. HHS




 designated period of time—benefits from a “presumption of
 causation” and is not required to demonstrate, by a prepon-
 derance of the evidence, that the vaccine was a “substantial
 factor” in causing the injury. See de Bazan, 

. That difference in proof is material: satisfying the
 applicable Table criteria is not equivalent to having proven
 actual causation. See Grant, 956 F.2d at 1148 (“Simple
 similarity to conditions or time periods listed in the Table
 is not sufficient evidence of causation . . . .” (quoting H.R.
 Rep. No. 99-908, at 15)); see also Routen v. West, 

 (Fed. Cir. 1998) (explaining that while a “pre-
 sumption affords a party, for whose benefit the presump-
 tion runs, the luxury of not having to produce specific
 evidence to establish the point at issue . . ., when the op-
 posing party puts in proof to the contrary of that provided
 by the presumption, and that proof meets the requisite
 level, the presumption disappears”); New York Life Ins. Co.
 v. Gamer, 

 (1938) (“[A] presumption is not
 evidence and may not be given weight as evidence.”) (col-
 lecting cases).
      Thus, upon satisfying his initial burden, the petitioner
 in a Table case earns a presumption of causation, which
 operates, not as proof of actual causation, but to “shift[]”
 the burden “to the [government] to prove that a factor un-
 related to the vaccination actually caused the illness, disa-
 bility, injury, or condition.” Pafford v. Sec’y of Health &
 Hum. Servs., 

, 1355 (Fed. Cir. 2006) (citation
 omitted). Accordingly, while the government in a Table
 case must affirmatively prove that a factor unrelated was
 the sole substantial cause by a preponderance of the evi-
 dence, it need not disprove that which was never affirma-
 tively proven, i.e., the vaccine as the cause in fact. See
 Walther, 

 (“[I]t would be unusual to re-
 quire a party to prove that ‘there is not a preponderance of
 the evidence,’ as our legal system rarely requires a party to
 prove a negative.”). White’s reliance on off-Table cases to
 argue that the government must eliminate the vaccine as
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 WHITE v. HHS                                                9



 causal, or as a substantial factor, see Appellant Br. 19–23
 (relying on Walther, Shyface, and de Bazan), is therefore
 misplaced because it treats White’s presumption as actual
 evidence of causation. See, e.g., id. at 23.
      White does, however, also offer a Table case, Knudsen,
 for the proposition that a presumption of causation stands
 in equipoise with evidence of actual causation. See Appel-
 lant Br. 37–40; id. at 40 (“After reviewing the evidence,
 [the] Federal Circuit should find, at minimum, that the ev-
 idence is equipoised between [White’s] and [the govern-
 ment’s] analyses of the facts and evidence; and therefore,
 [White] prevails” (citing Knudsen, 

)). But
 White misunderstands our holding in Knudsen and, in any
 event, fails to properly apply it to the facts in this case.
      In Knudsen, we vacated and remanded the decision of
 the Claims Court because “[t]he special master did not spe-
 cifically find whether the . . . evidence preponderated in fa-
 vor of alternative causation.” 35 F.3d at 550–51. We
 stated, with respect to the remand, that “[i]f the [govern-
 ment’s evidence of alternative causation] is seen in equi-
 poise [with the petitioner’s countervailing evidence], then
 the government has failed in its burden of persuasion and
 compensation must be awarded.” 

 (emphases
 added). In other words, contrary to White’s argument, we
 did not hold that a presumption of causation stood in equi-
 poise with proof of actual causation. Rather, we merely
 noted the uncontroversial principle that, if the govern-
 ment’s evidence of alternative causation stood in equipoise
 with the petitioner’s evidence on remand, then the govern-
 ment would not have met its burden of establishing alter-
 native causation by a preponderance of the evidence.
 Nothing in our holding suggested that the presumption it-
 self stood in equipoise with the government’s evidence, so
 White’s contention is wrong as a matter of law.
     What is more, this case is distinct from Knudsen on the
 facts. Here, unlike in Knudsen, the special master did
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 10                                                WHITE v. HHS




 “specifically find” that the parties’ competing “evidence
 preponderated in favor of alternative causation.” Compare
 Knudsen, 35 F.3d at 550–51 (explaining that “the special
 master did not specifically find” whether the evidence pre-
 ponderated one way or the other), with Special Master De-
 cision, at *17 (“[T]he record preponderantly supports [the
 government’s] contention that [White’s] demonstrated H.
 [i]nfluenza[e] infection was the more likely sole substantial
 factor causing [White’s] GBS . . . .”), and id. at *18, n.16 (“I
 conclude it ‘more likely than not’ that the vaccine is ex-
 cluded as causal.”). In reaching that conclusion, the special
 master first noted that White’s expert merely stated in
 “conclusory form” that “the flu vaccine was still likely . . . a
 substantial factor in [White’s] injury,” id. at *5, and relied
 on the vaccine being “presumed causative,” id. at *6 (cita-
 tion omitted). He then reviewed the relevant evidence to
 determine whether the government established a factor
 unrelated actually caused White’s injury. Specifically, he
 reviewed the medical literature and expert reports. See,
 e.g., id. at *17 (explaining that the “risk” of developing a
 GBS-related injury from vaccination “is consistently
 deemed lesser in comparison [to infection] (and in some
 studies unfounded).”); 2 id. (explaining that in some cases
 “[i]t has even been documented that vaccination might play
 a protective role against GBS.”). 3 Based on his review of


      2  F. DeStefano et al., Principal Controversies in Vac-
 cine Safety in the United States, CLINICAL INFECTIOUS
 DISEASES 1, 4 (2019), J.A. 499–504.
     3   J. Stowe et al., Investigation of the Temporal Asso-
 ciation of Guillain-Barré Syndrome with Influenza Vaccine
 and Influenza like Illness Using the United Kingdom Gen-
 eral Practice Research Database, 169 AM. J. EPIDEMIOLOGY
 OF 382, 385–86 (2008), J.A. 466–67; L. Grimaldi-Bensouda
 et al., Guillain-Barré Syndrome, Influenzalike Illnesses,
 and Influenza Vaccination During Seasons With and
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 WHITE v. HHS                                                11



 that medical literature, the special master drew the plau-
 sible inference that the government “has also shown that
 in the general context of vaccination and infection, vaccina-
 tion will usually be less likely causal (thus helping [the gov-
 ernment] to exclude the vaccine in this case as part of his
 enhanced burden to show factor unrelated).” Id. at *17.
     In addition to the medical literature, the special master
 also reviewed White’s medical records, which “establish[ed]
 that the infection . . . occurred far closer in time than vac-
 cination.” Id. at *18. From that, he drew the plausible in-
 ference that “[t]his medical history is not consistent with
 the vaccine playing even a contributory role to [White’s]
 GBS.” Id. We find that the special master’s decision to
 exclude the vaccine as a causal factor is grounded in the
 relevant record evidence and supported by plausible infer-
 ences. The conclusion is therefore not arbitrary and capri-
 cious.
                               B
       White next argues that the special master’s findings
 under the first and third prongs of Althen are arbitrary and
 capricious. Regarding prong one, the government’s burden
 was to show by preponderant evidence “a medical theory
 causally connecting the [factor unrelated] and the injury,”
 i.e., that the factor unrelated can cause the injury suffered.
 Althen, 

. White argues that the govern-
 ment did not provide a “sound and reliable medical or sci-
 entific explanation.” Appellant Br. 26 (citation omitted).
 Specifically, he argues that the government did not offer
 “sufficient evidence specific to the infection in question,
 [and] how it could cause GBS.” Id. at 29 (emphasis omit-
 ted). White contends that for the government to have pre-
 ponderantly established Althen prong one, it “needed to



 Without Circulating A/H1 N1 Viruses, 174 AM. J. OF
 EPIDEMIOLOGY 3, 326, J.A. 473.
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 12                                              WHITE v. HHS




 provide evidence of the biological mechanism of how the
 H[.] [i]nfluenza[e] could cause GBS.” Id. We disagree.
     “Althen makes clear that a claimant’s theory of causa-
 tion must be supported by a ‘reputable medical or scientific
 explanation.’” Andreu ex rel. Andreu v. Sec’y of Dep’t of
 Health & Hum. Servs., 

 (Fed. Cir. 2009)
 (quoting Althen, 

). Whether a theory of
 causation is “reputable” can depend on the scientific evi-
 dence. 

. But medical studies and data “must be
 viewed . . . not through the lens of the laboratorian, but in-
 stead from the vantage point of the Vaccine Act’s prepon-
 derant evidence standard,” which does not require
 “scientific certainty” or disproving “every possible ground
 of causation.” 

 (citation omitted); see Broekelschen v.
 Sec’y of Health & Hum. Servs., 

 (Fed.
 Cir. 2010); Moberly, 

; see also Lobo v. Dep’t
 of Just., 

, 1317 (Fed. Cir. 2025) (noting that
 “‘medical certainty’ . . . is more demanding than the pre-
 ponderance standard of more likely than not”). The gov-
 ernment, like a petitioner when the burden is on him, is
 therefore “not required to present proof of causation to the
 level of scientific certainty,” Moberly, 

, or
 to “provide conclusive evidence in the medical literature,”
 Andreu, 

. Nor is “identification and proof
 of specific biological mechanisms” required. Knudsen,
 

. Rather, “causation can be found in vaccine
 cases based on epidemiological evidence and the clinical
 picture.” 

 (citation omitted). White’s argument is there-
 fore premised on an incorrect articulation of our case law.
     Moreover, White has failed to demonstrate that the
 special master’s decision was arbitrary and capricious un-
 der the appropriate requirements for Althen prong one.
 The special master considered the relevant record evi-
 dence, see, e.g., Special Master Decision, at *17 (relying on
 an article stating that “[m]olecular mimicry and cross-re-
 active immune responses have also been identified after
 some types of preceding infection, including H.
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 WHITE v. HHS                                                13



 influenzae.”); 4 id. at *7, *17 (relying on a study that deter-
 mined that six GBS patients had elevated anti-H. influen-
 zae antibodies compared with only one in normal controls,
 suggesting an association), 5 and drew plausible inferences
 from said evidence, see, e.g., id. (finding that the evidence
 “demonstrat[ed] an association between the risk of GBS fol-
 lowing infection generally,” as well as a risk of GBS “spe-
 cific to the H. influenza[e] infection.”). We therefore see no
 reversible error regarding the special master’s analysis of
 the first prong of Althen. See Hines, 

 (“If
 the special master has considered the relevant evidence of
 record, drawn plausible inferences and articulated a ra-
 tional basis for the decision, reversible error will be ex-
 tremely difficult to demonstrate.”); see also Munn v. Sec’y
 of Dep’t of Health & Hum. Servs., 

 (Fed.
 Cir. 1992) (“[I]t is not then the role of this court to reweigh
 the factual evidence, or to assess whether the special mas-
 ter correctly evaluated the evidence.”).
     Regarding Althen prong three, the government’s bur-
 den was to show by preponderant evidence that there was
 a “proximate temporal relationship between [the factor un-
 related] and injury.” Althen, 

. White ar-
 gues that the “temporal association was determined,
 without any evidence proffered by [the government].” Ap-
 pellant Br. 35–37. He also takes issue with the special
 master’s analogy to another Claims Court case finding that
 12 days was a medically acceptable immune response time.
 

 at 35–36 (citing Randolph v. Sec’y of Health & Hum.



     4   P. van Doorn et al., Clinical Features, Pathogene-
 sis, and Treatment of Guillain-Barré Syndrome, 7 LANCET
 939, 941 (2008), J.A. 522.
      5  Y.Y. Ju et al., Haemophilus Influenzae as a Possi-
 ble Cause of Guillain-Barré Syndrome, 149 J.
 NEUROIMMUNOLOGY 160, 165–66 (2004) (“Ju”), J.A. 552–
 53.
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 14                                              WHITE v. HHS




 Servs., No. 15-146V, 

, at *23 (Fed. Cl.
 Nov. 12, 2021)). He argues that because “the case the [spe-
 cial master] relies upon does not support his conclusion,”
 since the onset here is only 10 days, and because “no dis-
 cussion by [the government’s] expert exists about an ‘adap-
 tive immune response’ in this case,” the special master
 could not “properly determine the temporal association in
 this case.” Id. at 36. Once again, we disagree.
      The burdened party must offer “preponderant proof
 that the onset of symptoms occurred within a timeframe
 for which, given the medical understanding of the disor-
 der’s etiology, it is medically acceptable to infer causation-
 in-fact.” de Bazan, 

 (citing Althen,
 

 (equating “proximate temporal relation-
 ship” with the phrase “medically-acceptable temporal rela-
 tionship”)). White’s argument that the special master
 made a finding based on “no evidence,” Appellant Br. 36, is
 not accurate and mischaracterizes the special master’s de-
 cision.
      The special master reviewed White’s clinical course
 and found that “[t]he medical records establish that the in-
 fection (which first manifested 10 days before [White’s]
 neurologic symptoms on December 10, 2017) occurred far
 closer in time than vaccination—but within a timeframe
 that would be reasonable for an antibody-driven, adaptive
 immune system autoimmune process to occur.” Special
 Master Decision, at *18. The special master also found “no
 record evidence of any close-in-time vaccine reaction.” 

 Furthermore, the special master reviewed the relevant
 medical literature offered by both experts, see 

 at *6–7
 (citing Ju, J.A. 547), and offered a reasoned explanation
 analogizing a 12-day timeframe for an onset of symptoms
 to the 10-day timeframe in this case, see 

 at *18 (citing
 Randolph, 

, at *23). Again, we will not
 second guess the special master’s reasoned assessment of
 the evidence and expert reports. See Munn, 

.
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 WHITE v. HHS                                               15



     Finally, White argues that the special master erred by
 using the term “likely” in describing White’s “likely infec-
 tion.” Appellant Br. 35–36 (citing Special Master Decision,
 at *18). He contends that “[l]ikely[] does not meet the ‘more
 likely than not’ standard of proof.” 

 at 35 n.9. But White
 takes the use of “likely” out of context. The special master
 used the term “likely” to account for the uncertainties in-
 herent in medical diagnoses, not to draw a causal compar-
 ison between the infection and vaccine. That is evident
 elsewhere in his decision, where he makes clear that he
 found that White did have an H. influenzae infection. See
 Special Master Decision, at *17 (explaining that “the med-
 ical records also establish that [White’s] H. influenzae in-
 fection likely ‘did cause’ his GBS”); 

 (explaining that the
 evidence—that White experienced a URI with a ten-day
 history of symptoms, his sputum findings positive for H.
 influenzae and that his chest X-ray findings showed wors-
 ening lung conditions—were persuasive); id. at *8 (“[A]t
 least 14 treaters associated [White’s] upper respiratory in-
 fection with the development of his GBS.”). He also clearly
 articulated and applied the “more likely than not” standard
 to the government’s evidence and argument. See, e.g., Spe-
 cial Master Decision, at *18 n.16 (“I emphasize again: this
 determination is the result of the preponderance standard.
 I conclude it ‘more likely than not’ that the vaccine is ex-
 cluded as causal.”).
     In sum, the special master’s conclusion that “the record
 preponderantly supports [the government’s] contention
 that [White’s] demonstrated H. [i]nfluenza[e] infection was
 the more likely sole substantial factor causing [White’s]
 GBS,” id. at *17, reflects a careful review of the record evi-
 dence, including the medical literature and expert reports,
 and is therefore not arbitrary and capricious.
                         CONCLUSION
     We have considered White’s remaining arguments and
 find them unpersuasive. For the foregoing reasons, we
Case: 24-1372    Document: 37     Page: 16    Filed: 08/27/2025




 16                                             WHITE v. HHS




 conclude that the special master’s decision is in accordance
 with the law and his findings are not arbitrary and capri-
 cious. Accordingly, we affirm the Claims Court’s upholding
 of the special master’s denial of White’s claim for compen-
 sation under the Vaccine Act.
                        AFFIRMED
                           COSTS
 No costs.