Hvor effektive var mrna-vaccinerne imod Covid-indlæggelser i Danmark?

Jeg støder ganske ofte på den opfattelse at mrna-vaccinerne imod corona ingen effekt har haft.

Men det er en opfattelse som jeg ikke har kunnet finde noget videnskabeligt belæg for.

Der er mange undersøgelser af forskellig art fra forskellige lande af vaccinernes effektivitet, og jeg har endnu ikke kunnet finde nogen som ingen effekt har vist. Det skal siges at jeg her har set på opsamlingerne i meta-analyserne.

Til gengæld synes billedet generelt at være at effekten af vaccinerne aftager med tiden, som man ville forvente, og at effekten imod omikron har været mindre end mod alpha og delta.

I Danmark udkom der for to måneder siden et studie af vaccinernes effekt på henholdsvis infektion og indlæggelse.

Her vil jeg se på tallene for indlæggelse.

Hovedparten af danskere har modtaget tre doser af mRNA-vaccinerne, så lad os se hvad forskerne skriver om effekten af det:

For both age groups, small absolute differences were observed in the VE estimates of 3 doses against COVID-19 hospitalization between the Delta or Omicron variant. However, it is difficult to compare the estimates between the Delta and Omicron variant because the available time interval after vaccination during the Delta period was shorter. Among the relatively small group of individuals aged 18 to 59 years who were vaccinated with a third dose in the autumn of 2021, VE against COVID-19 hospitalization following infection with the Delta variant was 93.2% (95% CI: 81.7; 97.5) 14 to 30 days and 61.5% (95% CI: 23.4; 80.6) 31 to 60 days since vaccination. In individuals aged 60 years or above, VE against COVID-19 hospitalization following infection with the Delta variant was 97.2% (95% CI: 94.6; 98.5) 14 to 30 days and 91.7% (95% CI: 78.7; 96.7) 61 to 90 days since vaccination. In comparison, in individuals aged 18 to 59 years, VE against COVID-19 hospitalization following infection with the Omicron variant was 95.5% (95% CI: 93.5; 96.8) 14 to 30 days since vaccination. From then on, a gradual decline in VE was observed reaching 67.5% (95% CI: 50.4; 78.7) 91 to 120 days since vaccination. A smaller decrease in the VE against COVID-19 hospitalization following infection with the Omicron variant was observed among individuals aged 60 years or above with an estimated VE of 96.7% (95% CI: 95.6; 97.6) 14 to 30 days and 83.3% (95% CI: 77.3; 87.8) >120 days since vaccination (Table 5 and Fig 4).

Det er en ganske høj effektiviteter, ikke mindst hvis man sammenligner med for eksempel vacciner imod influenza.

Og forskerne samlede konklusion er da også optimistisk:

Two vaccine doses provided high protection against SARS-CoV-2 infection and COVID-19 hospitalization with the Alpha and Delta variants with protection, notably against infection, waning over time. Two vaccine doses provided only limited and short-lived protection against SARS-CoV-2 infection with Omicron. However, the protection against COVID-19 hospitalization following Omicron SARS-CoV-2 infection was higher. The third vaccine dose substantially increased the level and duration of protection against infection with the Omicron variant and provided a high level of sustained protection against COVID-19 hospitalization among the +60-year-olds.

Hvad er VE - vaccineeffektivitet

Vaccineeffektivitet måler effekten af en vaccine i forhold til om den påvirker risikoen for at pådrage sig en sygdom, blive indlagt på grund af en sygdom eller dø af en sygdom.

VE er udtryk for den forskel som en vaccine gør.

Hvis for eksempel en ud af hundrede i en vaccineret gruppe indlægges med en given sygdom der vaccineres imod, mens hver 10. uden vaccination gør, så udregnes VE:

VE = ((0,1 - 0,01)/0,1) * 100 procent = 90 procent

Principielt kan VE blive negativ hvis vaccinationen gør at flere bliver indlagt end uden indgriben.

Vaccineeffektivitet bruges i obersevationsstudier, mens man på engelsk skelner mellem vaccine efficacy for kliniske studier hvor man har en placebo, og vaccine effectiveness for observationsstuider hvor man ikke har.

Kilde

Vaccine effectiveness against SARS-CoV-2 infection or COVID-19 hospitalization with the Alpha, Delta, or Omicron SARS-CoV-2 variant: A nationwide Danish cohort study Gram MA, Emborg HD, Schelde AB, Friis NU, Nielsen KF, et al. (2022) Vaccine effectiveness against SARS-CoV-2 infection or COVID-19 hospitalization with the Alpha, Delta, or Omicron SARS-CoV-2 variant: A nationwide Danish cohort study. PLOS Medicine 19(9): e1003992. https://doi.org/10.1371/journal.pmed.1003992