9 August 2023 Episode 342 Strategic masking and new variant EG.5.1

Wed, 08/09/2023 - 15:46

Episode 342: Update on COVID: strategic masking and “Eris” variant

Dear colleagues,

Just a small episode, building on diverse papers that you might have seen or missed.

Par 1 Strategic masking for respiratory diseases

Ep 342-1:  Michael Klompas NEJM 20 July:

While COVID is no longer an urgent threat, it is surprising to see that the health care sector has completely abandoned face masks, since any respiratory infection can have serious consequences for vulnerable patients, especially in hospitals and those infections can be transmitted to them from seemingly healthy persons.  

Therefore, it seems reasonable to strongly advice or impose face mask wearing by patients, staff and visitors: 

  • In all health care facilities during the specific months of the year that there is high transmission of respiratory viruses (i.e. late autumn and winter).  
  • Year-round masking for clinical interactions involving patients at particularly high risk for poor outcomes: e.g. profound immunosuppression, such as those undergoing hematopoietic stem-cell transplantation, treatment with anti-CD20 agents, or heart or lung transplantation.

Par 2 A new variant EG.5.1 (Nickname ERIS)

Ep 342-2: Tweet from Yonlung Cao 5 Aug 2023



Ep 342-3: Eric Topol Ground Truth 6 August confirms

This new variant EG.5.1 is a “combo flip”, because of adjacent mutations in the spike L455F and F456L positions, in the backbone of XBB.1.5. It’s being called a FLip because both mutations are between F (phenylalanine) and L (leucine) : one L to F, the other F to L


As shown by Cao in Ep 342-2 above:

  1. EG.1.5 is a strong escape mutant: there is a drop of neutralizing antibody levels (Plasma NT50) when the F456L mutation is added to XBB.1.5 and for EG.5.1 which carries both mutations. This very weak neutralizing activity is measured in serum from subjects who were vaccinated, but experienced breakthrough infection with BA.5 AND with either XBB.1.5 or XBB.1.16.  EG.5.1
  2. High affinity for ACE-2 receptor


The new variant is rising in  US, but also in Brazil and Spain






  1. At present unclear whether this will become a new wave worldwide and whether it will be more pathogenic.  There is a new rise in hospitalizations, but not yet clear if it relates to EG.5.1.
  2. It is clear that EG.5.1 virus can escape from BA.5 immunity, since there are 15 mutations, but there are  only two mutations as compared to XBB.1.5.  So there is a good chance that the XBB.1.5 booster that will be ready in the Fall will induce immunity.  IF the virus has not already spread around by that time.




Note: this relative optimism of Eric Topol about the potential of XBB.1.5 based vaccines to protect against EG.5.1 is at first view NOT consistent with the data of Cao, who shows that breakthrough infection with BA.5 + reinfection with XBB is associated with very weak neutralization titers towards EG.5.1


Ep 343-4: Mary Kekatos ABC News 8 August  the latest figures



Ep 343-5: Maryam Zakir-Hussain Independent 5 Aug about EG.5.1 (Eris) in UK


Symptoms of Eris variant are generally mild: rhinitis, sore throat, fatigue, headache


Epidemiology: According to the UKHSA (Health Security Agency), Eris was initially raised as a signal in monitoring on 3 July 2023 due to increased reports internationally, particularly in Asia.

In the week beginning 10 July 2023, 11.8 per cent of UK sequences had been classified as Eris (data as of 27 July2023). The latest data suggests it now accounts for 14.6 percent of cases.


Potential impact: UK experts are divided


  • Prof Christina Pagel  (Clinical Operational Research University College) believes this variant will start a new wave, especially in Sept when schools are reopening  and we will spend more time inside.  Most people have had their last vaccine or infection many moths ago and therefore immunity is waning.


  • Professor Azeem Majeed (Imperial College Primary Care Public Health) downplayed the concerns about the Eris variant.
    • I don’t feel that people should be unduly worried by the recent increase in Covid-19 cases. Case numbers willfluctuate and there will be periods when the number ofcases in the UK increases
    • EG.5.1 is a version of the Omicron variant that appeared in the UK at the end of 2021, and WHO hasdesignated EG.5 as a variant under monitoring (VUM) but notas a variant of concern (VOC).


Ep 343-6: ECDC remains rather vague, but latest report from 30 July


EG.5.1 is not mentioned. It is considered as one of many XBB.1.5 descendants, namely of XBB.1.9.2 which has already the additional mutation F456L. If you add L455F to XBB.1.9.2, you have EG.5.1



In conclusion:


  • I would hope that the health sector complies with the advice on “Strategic masking”, especially to protect vulnerable patients. In my opinion, wearing a face mask should be rather standard in a health care setting, just like we wear a seatbelt in our car and a helmet when biking.  
  • The new variant EG.5.1 deserves careful monitoring, but there is no reason for panic, as there are no signs of seriously increased severity of disease as yet. Unfortunately, based on the data by Cao, it is likely  that the XBB-based vaccine booster in the Fall will not be able to fully protect against EG.5.1 infection (low antibody neutralization), but we can reasonably hope that the T cell immunity will sufficiently be boosted to protect vulnerable patients against severe disease.


Best wishes,