Are Covid-19 treatments working? – Expert Q&A

Timely treatment for Covid-19 is front of mind for many people, in light of NZ's mounting hospitalisation and death statistics.

Now that Aotearoa has 960 people in hospital and a steepening death curve from Covid-19, how are people being treated for the disease at present? What's working against the Omicron variant (and what's not) - and when are new treatments anticipated to arrive in the country?

The Science Media Centre asked experts for an update on Covid-19 treatments in New Zealand.

Dr Colin McArthur, Intensive Care Specialist, Auckland City Hospital, comments:

What Covid-19 treatments are being used in NZ now, and how are they working out?

“Treatments with proven efficacy for COVID-19 are in two broad areas: those directed against the virus itself (antivirals) and those which modify the body’s response to the infection (immune modulators). In general, antiviral treatments need to be given early (within 5 to 7 days of symptom onset) to be of benefit, while immune-modulating treatments are only appropriate for patients who are hospitalised and need oxygen or higher levels of breathing support.

"In New Zealand, we have the intravenous antiviral drug remdesivir, which has been used for patients hospitalised within the first 7 days of illness. It is also effective at reducing the risk of hospitalisation in those at high risk, but early administration of an intravenous drug outside of hospital is difficult. Processes are being established now to provide this treatment in the community for those at the greatest risk of deterioration, as supplies are limited.

"The oral antiviral agents, Paxlovid (a combination of nirmatrelvir and ritonavir) and molnupiravir, are also of benefit to those at higher risk of hospitalisation, and are expected to be available over the next few months. These treatments need to be commenced within 5 days of symptom onset to have an effect - and so good systems for early diagnosis of COVID-19 after symptom onset, and prompt prescription and dispensing, will be important.

"Another treatment aimed at the virus are monoclonal antibodies, which help the body identify and eliminate the virus. We have supplies of Ronapreve (a combination of casirivimab and imdevimab) in New Zealand currently, but unfortunately although this is effective against earlier variants such as Delta, it is not active against Omicron.

"Some monoclonal antibodies such as sotrovimab do retain activity against Omicron, but these are understandably in high demand globally and are not yet available here. These treatments are also given by injection and their use pre-hospital where they are most effective has similar challenges to remdesivir (explained above)."

Note: Australian researchers have also found Sotrovimab may cause drug-resistant mutation. They say this treatment's increased use requires increased surveillance to help detect potential resistance earlier.

What triggers a need for Covid-19 treatment?

"Treatment in hospital depends on a patient’s severity and rate of progression. Those with mild disease need no specific COVID treatments, but low doses of blood-thinning treatment may be commenced because COVID-19 can cause problems with blood clots. When there is evidence of lung inflammation (pneumonitis), more intense blood-thinning therapy may be used.

"Once there is a sustained need for additional oxygen, immune-modulating treatment is begun, initially steroid treatment with dexamethasone. If there is further deterioration, tocilizumab, or more recently barcitininb, is added. Both of these drugs block parts of the inflammatory response. As lung function worsens, higher flows of oxygen are provided. Additional assistance with breathing can be given with a sealed mask to provide additional support, and in some severe cases mechanical ventilation - via a tube into the lungs - may be required."

How effective are current treatments against Omicron?

"An important caveat with specific COVID treatments is that we don’t know if the Omicron - or other variants - have an impact on their effectiveness because all were studied before Omicron came on the scene. This is a known issue for the monoclonal antibodies, many of which are less effective because they were designed to attach to the original SARS-CoV-2 spike protein. We also know that Omicron is a less severe variant and so treatments given to reduce the risk of severe disease need to be highly-targeted to those at the very highest risk to be beneficial. However, although not known for certain, it is less likely that other treatments - such as the antiviral drugs and especially the immune-modulation therapies - will lose effectiveness."

No conflict of interest declared.