No 47 - 2022

The variant-updated COVID-19 booster vaccines are not approved for primary vaccination
Chlamydia 2019-2021

The variant-updated COVID-19 booster vaccines are not approved for primary vaccination

Statens Serum Institut has received several enquiries concerning the use of the variant-updated COVID-19 booster vaccines and therefore draw attention to the following:

The new variant-updated COVID-19 vaccines, Comirnaty Original/Omicron BA.1 and BA.4-5 and Spikevax Original/Omicron BA.1 and BA.4-5, have been approved only for booster vaccination once primary vaccination has been concluded using a monovalent Comirnaty or Spikevax vaccine. Therefore, Statens Serum Institut recommends that citizens who have not initiated or concluded their primary vaccination course are referred to a vaccination centre where the monovalent COVID-19 vaccines will still be available.

(Statens Serum Institut)

Chlamydia 2019-2021

  • 2021 recorded 36,632 laboratory-confirmed chlamydia cases (10% more than in 2018).
  • A total of 272,809 people were tested (1% fewer than in 2018).
  • The number of tested persons and chlamydia cases declined in 2020 compared with 2019, most likely due to the COVID-19 pandemic.
  • Men comprised 42% of all detected chlamydia cases, whereas the positive rate was higher among men (20%) than among women (11%).
  • The chlamydia incidence among young people aged 15-29 increased compared with 2018, even though a decline was recorded in 2020.
  • For both sexes, the incidence of tested persons was lower in 2021 than in 2018 in most age groups, but increased for boys aged 15-24 years and girls aged 10-24 years and < 1 year.
  • For both sexes, the positive rate among tested persons increased from 2018 to 2021 and the greatest percentage increase was observed among 15-19-year-olds.
  • Furthermore, also for both sexes, in the age group 10-14 years, the number of cases per 100,000 increased in 2021 compared with 2018.
  • A total of 86% of all chlamydia cases are observed in the 15-29-year age group, which should wherefore be encouraged to be extra attentive to safe sex; and patients with positive tests should be instructed to undertake partner tracing.
  • As the test activity is lower among men than among women and as men have a higher positive rate, men in the 15-29-year age group in particular should be encouraged to be tested.
  • The number of rectal chlamydia cases in 2021 (1,294) was 46% higher than that observed in 2018 (889).
  • The share of men with anorectal chlamydia who were tested for LGV has increased; and in 2021, it comprised 59% (53% in 2018), whereas the total number of detected LGV cases was 16 in 2021 and 64 in 2018.
  • Since 2019, doxycycline has been first-choice treatment for uncomplicated C. trachomatis. The change in the treatment regime was introduced because Denmark has recorded a high occurrence of azithromycin resistance among Mycoplasma (M.) genitalium, which is believed to be caused by the previous use of azithromycin as first-choice treatment of C. trachomatis.

As in the preceding years, the data used to prepare this description of the incidence of chlamydia in the 2019-2021 period were collected via the Danish Microbiology Database (MiBa) and comprise all positive and negative test results for oculo-genital infection caused by Chlamydia trachomatis.

A detailed epidemiological description of the incidence of chlamydia from 2019 to 2021 is available here.

Since 2018, the number of persons tested for chlamydia has declined by 1.1%, whereas the number of detected chlamydia cases has increased by 9.6%. The positive rate has increased by 1.3 percentage points to 13.4%. Compared with 2019, the number of tested persons and detected chlamydia cases declined in 2020, probably because of the COVID-19 pandemic. Notably, a considerable decline was observed in the number of tested persons and chlamydia cases in the months of February, March and April, whereas the positive rate followed the curve from 2019.

Apart from in the age groups < 1 year and 45+ years, more than twice as many women as men are tested for chlamydia. Even so, the positive rate among men is higher than that observed for women in nearly all age groups. In 2021, the male share of detected chlamydia cases comprised 42%, which is in line with the figures recorded for 2018. Even though the share has followed a steadily increasing trend, the distribution is inexpedient, underlining the importance of increased testing activity among men.

Overall in Denmark and for nearly all Danish areas, considerably more men were tested for rectal chlamydia in 2021 than in 2018. Furthermore, the number of rectal chlamydia cases increased by 46% to 1,294, whereas the positive rate declined by 0.9 percentage points to 19% compared with 2018. A clear increase was observed in the number of cases in the Central Denmark Region, whereas the number of cases in the North Denmark Region increased considerably compared with 2018. In 2020, the number of tested men and detected cases remained largely unchanged compared with 2019. Among men who had rectal chlamydia detected, 59% also underwent LGV testing; an increase by six percentage points since 2018. However, the occurrence of men who have anorectal LGV detected has declined by 72% since 2018, reaching 16 cases in 2021. It should be stressed that persons with rectal chlamydia should be tested for HIV, syphilis and gonorrhoea; and the sample material should be tested for the variant of C. trachomatis that may cause LGV, EPI-NEWS 20/2008.

A total of 86% of all chlamydia cases are seen in 15-29-year-olds. However, the number of persons tested in this age group is considerably lower among men than among women. The preventive measures therefore need to be strengthened through more information about sexual behaviour, increased sampling activity and partner tracing once chlamydia has been detected.

Previously, Denmark recommended azithromycin 1g given orally as a single dose for treatment of uncomplicated chlamydia. However, double infection with C. trachomatis and Mycoplasmagenitalium is probably relatively frequent; and as a considerably higher ocurrence of azithromycin resistance was found among M. genitalium in Denmark than in Sweden, where doxycycline is used for chlamydia treatment, Denmark decided to change the recommendation regarding chlamydia treatment in 2019. First-line treatment of uncomplicated chlamydia including uncomplicated rectal chlamydia was then changed to orally administered doxycycline 100 mg x 2 for seven days. In case of rectal LGV, the same dose is used, but for 21 days. Guidelines on the treatment of chlamydia in pregnant women and persons with complicated chlamydia cases, including epididymitis and salpingitis, are available (in Danish language) in the guidelines published by the Danish Dermatological Society on sexually transmittable infections (DDS-vejledning-SOI_version-1.1_22.12.2021.pdf).

In EPI-NEWS 38/2019, a mutated variant was reported of C. trachomatis (FI-nvCT (C1515T)) in Finland that could not be detected using a very common diagnostic method (Aptima Combo 2® Assay; Hologic Inc., USA) (AC2). Testing of Danish chlamydia samples showed that the FI-nvCT variant was rare, but that a new C. trachomatis AC2 diagnostic-escape variant (nvCT-G1523A) was more common. This variant was previously detected in the UK and Norway. The updated AS2 analysis now comprises both variants. It is important to stress that other methods, e.g. Aptima CT® Assay (Hologic Inc., USA) can detect C. trachomatis despite the mentioned mutations.

(A. Skafte-Holm, T. Roland Pedersen, S. Hoffmann, Department of Bacteria, Parasites & Fungi; K.D. Bjerre, Data Integration and Analysis).

23 November 2022