Research paper - Corona reinfection is rare, but frequently occurs in those over 65 years old

 Recently CNN.co.jp reported the following:

コロナ再感染はまれも、６５歳以上に多発　研究論文

2021.03.18 Thu posted at 16:55 JST

 （ＣＮＮ） 英医学誌「ランセット」は１７日、新型コロナウイルスの再感染の発生は比較的まれなものの、６５歳以上の人間でより多く見られるとの研究論文を掲載した。

 北欧デンマークの感染症疫学・予防担当局の研究者たちによると、感染を体験した大半の人間は約半年間、再感染を免れる兆候があるが、再度の感染を被った年齢別の層を見た場合、６５歳以上が目立ったとした。

 今回の研究では、昨年９月から１２月３１日までの新型コロナの第２波の到来中に４００万人を対象に再感染率を調査し、同年３～５月期の第１波時のデータと比較した。この結果、第１波時に陽性反応を示した１万１０６８人のうち、第２波で２度目の感染が判明したのは７２人のみだったという。

 ただ、高齢層が再感染を防ぎ得る比率は約４７％で、若年層の約８０％と大きな差が出た。加齢と共に人間の免疫能力は弱体化するので、この格差は全くの予想外の結果ではないとも説明した。

 今回とは違う他の研究結果によると、再感染率は１％以下で、一度感染すればその免疫能力は５～６カ月維持される可能性もある。

 デンマークの感染症疫学・予防担当局の研究者たちは今回の研究結果は、誰もがワクチン接種を受ける必要性を改めて示したとし、特により深刻な新型コロナの症状が出やすいとみられる高齢者には重要だと強調した。

  Translation

(CNN) The British medical journal "Lancet" published a research paper on the 17^th saying that re-infection of the new coronavirus would be relatively rare, but more common in humans aged 65 and over.

According to researchers at the Danish Department of Infectious Disease Epidemiology and Prevention in Scandinavia, most people who had experienced the infection showed signs of avoiding reinfection for about half a year; but if looking at the age group of that who have been re-infected, people aged 65 and over were conspicuous.

In this study, the reinfection rate was investigated by comparing the data of the 4 million people during the arrival of the second wave of the new corona from September to December 31 last year, and during the first wave in the March-May period of the same year. As a result, among the 11,068 people who tested positive during the first wave, only 72 were found to be infected for the second time in the second wave.

However, the ratio that the elderly could prevent reinfection was about 47%, which was a big difference from about 80% among the young. This coming to light of this disparity was not a completely unexpected result, as human immune capacity could weaken with age.

According to other studies different from this one, the reinfection rate was less than 1%; and once infected, its immune ability might be maintained for 5 to 6 months.

Researchers at the Danish Department of Infectious Disease Epidemiology and Prevention reiterated the need for vaccination for everyone. It emphasized that it was important especially for older people who were more likely to have more serious symptoms of the new corona.

              So, as human immune capacity weakens with age, older people are more likely to have more serious symptoms to Covid-19. It is interesting to note that the immune ability may be maintained for 5 to 6 months only. If this is the case, Covid-19 vaccination would be a repeating and regular event for many years to come in all the countries.