Given a passage with a context and an answer, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

Q: Context: Replacing live-attenuated oral poliovirus vaccines (OPV) with inactivated poliovirus vaccines (IPV) is part of the global strategy to eradicate poliomyelitis. China was declared polio-free in 2000 but continues to record cases of vaccine-associated-poliomyelitis and vaccine-derived-poliovirus outbreaks. Two pilot safety studies and two larger immunogenicity trials evaluated the non-inferiority of IPV (Poliorix™️, GSK Vaccines, Belgium) versus OPV in infants and booster vaccination in toddlers primed with either IPV or OPV in China.', 'In pilot safety studies, 25 infants received 3-dose IPV primary vaccination (Study A, www.clinicaltrial.gov NCT00937404) and 25 received an IPV booster after priming with three OPV doses (Study B, NCT01021293). In the randomised, controlled immunogenicity and safety trial (Study C, NCT00920439), infants received 3-dose primary vaccination with IPV (N=541) or OPV (N=535) at 2,3,4 months of age, and a booster IPV dose at 18-24 months (N=470, Study D, NCT01323647: extension of study C). Blood samples were collected before and one month post-dose-3 and booster. Reactogenicity was assessed using diary cards. Serious adverse events (SAEs) were captured throughout each study.', 'Study A and B showed that IPV priming and IPV boosting (after OPV) was safe. Study C: One month post-dose-3, all IPV and 98.3% OPV recipients had seroprotective antibody titres towards each poliovirus type. The immune response elicited by IPV was non-inferior to Chinese OPV. Seroprotective antibody titres persisted in 94.7% IPV and 96.1% OPV recipients at 18-24 months (Study D). IPV had a clinically acceptable safety profile in all studies. Grade 3 local and systemic reactions were uncommon. No SAEs were related to IPV administration.
Answer: Trivalent IPV is non-inferior to OPV in terms of seroprotection (in the Chinese vaccination schedule) in infant and toddlers, with a clinically acceptable safety profile.

A: Is primary and booster vaccination with an inactivated poliovirus vaccine ( IPV ) immunogenic and well-tolerated in infants and toddlers in China?
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Q: Context: Nonviral vectors based on polyethylenimine (PEI) usually contain an excess of PEI that is not complexed to DNA. Since unbound PEI contributes to cellular and systemic toxicity, purification of polyplexes from unbound PEI is desirable.', 'Size exclusion chromatography (SEC) was used to purify PEI polyplexes of free PEI. Transfection properties of purified polyplexes and the effect of free PEI on gene delivery were studied in vitro and in vivo after systemic application into mice.', 'SEC did not change the size and zeta-potential of polyplexes. Independent of the amount of PEI used for complex formation, purified PEI polyplexes had the same final PEI nitrogen/DNA phosphate ratio of 2.5. Notably, purified PEI polyplexes demonstrated low cellular and systemic toxicity. High transfection efficiency was achieved with purified polyplexes at high DNA concentrations (8-15 microg/ml). At low DNA concentrations (2-4 microg/ml) gene transfer with purified particles was less efficient than with polyplexes containing free PEI both in vitro and in vivo. Mechanistic studies showed that free PEI partly blocked cellular association of DNA complexes but was essential for the following intracellular gene delivery. Adding free PEI to cells treated with purified particles with a delay of up to 4 h resulted in significantly enhanced transfection efficiency compared with non-purified particles or purified particles without free PEI.
Answer: This study presents an efficient method to remove free PEI from PEI polyplexes by SEC. Our results from transfection experiments demonstrate that free PEI substantially contributes to efficient gene expression but also mediates toxic effects in a dose-dependent manner. Purified polyplexes without free PEI have to be applied at increased concentrations to achieve high transfection levels, but exhibit a greatly improved toxicity profile.

A: Does purification of polyethylenimine polyplexes highlight the role of free polycations in gene transfer?
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Q: Context: Parathyroidectomy (PTx) is the most successful treatment for advanced secondary hyperparathyroidism (2HPT) not responsive to medical treatment. However, persistent HPT remains problematic after PTx if some glands remain. The clinical course in patients with persistent 2HPT was evaluated to clarify the risk for re-operation after PTx.', 'Between March 1981 and December 2001, initial total PTx with forearm autograft were performed in 1156 uraemic patients. Persistent HPT cases were defined as those in which the lowest post-operative intact parathyroid hormone (i-PTH) concentration was >60 pg/ml, and patients were classified into groups A, B and C, with i-PTH concentrations of >or=500, 300-500 and 60-300 pg/ml, respectively. These patients were followed for 7-234 months after PTx.', 'Persistent HPT was identified in 49/1156 patients (4.2%), with nine cases in group A, 10 in group B and 30 in group C. Re-operation was required in 21/49 (42.8%) cases, and in seven of these the last i-PTH concentration was >or=500 pg/ml. All cases in group A required re-operation. In group C, 11/30 (36.7%) patients required re-operation. The missed glands removed at re-operation were supernumerary in 14 cases, and located in the mediastinum in 13 cases. The frequency of advanced HPT and re-operation was not negligible.
Answer: To prevent persistent 2HPT, all parathyroid glands must be found and resected during the initial operation. Even if small parathyroid glands remain, there is a risk of progression. Complete PTx is the first treatment choice for advanced 2HPT.

A:
Is re-operation frequently required when parathyroid glands remain after initial parathyroidectomy for advanced secondary hyperparathyroidism in uraemic patients?
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