Expert panel answers your Omicron questions

The University of Auckland has many medical experts who share their knowledge of Omicron. In March 2022, Professor John Fraser, Associate Professor Helen Petousis-Harris, Honorary Professor Nikki Turner and Professor Papaarangi Reid were joined by Dr Stephen Ritchie, an infectious diseases physician with the Auckland District Health Board, to answer your Omicron questions. 

Should we still be trying to avoid Omicron or give in to the inevitable and get it over with?
At a community level we can’t cope with everyone getting sick at once. There’s an idea that Omicron is a mild illness, but at an individual level we don’t know who will have a more severe experience of the virus – or who will be affected by Long Covid. ‘Mild disease’ might not actually be that mild. Infectious diseases are best avoided and avoiding Covid means being vaccinated and avoiding exposure – if you are sick, stay home and do what you can to avoid coming into contact with others.

How infectious and virulent is Omicron, compared to other strains of Covid?
In March, the case numbers for the nation were around 400,000, which is about 6-7 percent of the population of New Zealand – and that occurred in a little over a month. Omicron is a new strain of SARS and has now outcompeted every other SARS-CoV-2 strain on the planet. Delta had an R number (the average number of people that one infected person will pass on a virus to) of about five. Omicron has an R number of about 20. Viruses evolve to increase their fitness, and this often means trading virulence in favour of transmission. This seems to be exactly what Omicron has done. It is more infectious but less virulent than Delta and for most people Omicron causes mild symptoms characteristic of an uncomplicated upper respiratory tract infection. Data from overseas show that only 1.1 percent of cases with Omicron require hospitalisation. For Delta that was about ten percent.

What is the latest research on vaccine effectiveness for Delta and Omicron?
For the first two doses, the drop-off in effectiveness against symptomatic disease is much quicker with Omicron than Delta – hence the importance of the booster. But the data is showing that even with Omicron, you are still getting good protection for four to six months after vaccination against severe disease.

Why is one person’s experience of Omicron infection different from another’s?
Most of the unpleasant effects people experience from a viral infection, such as fever, headache, aching limbs and nausea, are actually a result of your immune response releasing powerful soluble mediators that affect all parts of your body. Feeling sick is a great way of telling you that you have an infection and you need to isolate. The type and extent of your own personal response is a consequence of the inherent variation that exists across the entire population. Every person’s immune system is genetically unique and there are no two the same, except identical twins. Environmental factors and individual health status also influence how sick you feel.

If someone is a household contact but manages to avoid getting Covid does that mean their immunity is good and they are less likely to catch it another time?
We can’t yet answer that. What we know from household studies is that up to 70 percent of the household will catch it. But we don’t know if the other 30 percent did catch it and were asymptomatic or actually managed not to be exposed. Some may not have been infected, so they won’t have had an immune response, which means they are still immune naïve.

Is Omicron still spread by surfaces or just by air transmission?
It definitely can be spread from a surface that has been contaminated by someone else’s droplets – tiny particles of mucous that contain the virus which emerge when we cough and sneeze. But the dominant form of transmission is from people who are coughing and sneezing and therefore it’s inhaled into the upper airways.

Should we have boosters for those who are vulnerable or immune suppressed?
The questions that arise are, who is at high risk, when is their protection against severe disease likely to drop off, and when are they likely to need boosting? Different decisions are being made around the world, but it is looking as though those who are more at risk, particularly frail, elderly people with significant medical issues, may well need boosting as their protection drops.

If you get Covid, how strong is your immunity afterwards and for how long?
Once you get the disease you do have immunity for a period of time, but we know that you can get Omicron again. This is not a surprise. We know that with respiratory illness, your immunity will wane over time, and you can repeatedly get infections. But data and studies are showing that vaccination is giving better immunity than disease, and a combination of vaccination and natural infection provides much broader protection over all the other SARS-CoV-2 variants.

Do vaccinated people shed less of a viral load if they get Covid than those who aren’t?
People who are unvaccinated are more likely to be severely symptomatic and therefore more likely to spread viral load. People who are vaccinated are likely to be infectious for a shorter period.

What is the likelihood of further variants, and will they be more or less serious?
Viruses are always evolving, and they do so by mutation. Typically, they evolve to be more fit. What viruses really want to do, more than anything else, is transmit. They’re not interested in being more virulent; making people sick works against the virus because if people get sick and go to bed they don’t transmit. Any strain that increases transmission by reducing the virulence is considered to be more successful. Omicron is a very successful strain and the likelihood of it reverting to a more virulent strain is becoming less likely. Remember, Omicron has overtaken every other single variant in the world in six months, so it is going to take a very special variant to outcompete it.

For those with respiratory conditions such as asthma, how practical is it to avoid Covid when others begin to relax their behaviours?
We need a better respiratory strategy. People should protect themselves and their communities more generally from all respiratory illnesses. This means improving our approach to influenza as well as Covid, to protect the people most at risk.

WATCH THE FULL OMICRON Q AND A BELOW