{"id":32561,"date":"2021-09-10T12:12:22","date_gmt":"2021-09-10T08:12:22","guid":{"rendered":"http:\/\/www.mauritiustimes.com\/mt\/?p=32561"},"modified":"2021-09-10T12:12:45","modified_gmt":"2021-09-10T08:12:45","slug":"why-are-we-seeing-more-covid-cases-in-fully-vaccinated-people-an-expert-explains","status":"publish","type":"post","link":"https:\/\/www.mauritiustimes.com\/mt\/why-are-we-seeing-more-covid-cases-in-fully-vaccinated-people-an-expert-explains\/","title":{"rendered":"Why are we seeing more COVID cases in fully vaccinated people? An expert explains"},"content":{"rendered":"

\"\"<\/em><\/h4>\n

<\/h4>\n

\u2018Breakthrough\u2019 infections can happen because of waning immunity or high viral doses. But our vaccines are still
\nexcellent at preventing severe disease and death<\/em><\/span><\/h4>\n

\"\"Naron Sangnak\/EPA\/AAP<\/span><\/span><\/p>\n

Many people are worried about reports of \u201cbreakthrough\u201d Covid-19 infections overseas, from places like\u00a0Israel\u00a0and\u00a0the United States.<\/span><\/p>\n

A breakthrough infection is when someone tests positive for Covid after being fully vaccinated, regardless of symptoms.<\/span><\/p>\n

The good news is most breakthrough infections usually\u00a0result in mild symptoms or none at all, which shows us that vaccines are doing exactly what they\u2019re supposed to do \u2014 protecting us from severe disease and death. Vaccines aren\u2019t designed to protect us from getting infected at all (known as \u201csterilising immunity\u201d).<\/span><\/p>\n

People with breakthrough infections\u00a0can go on to infect others. Preliminary evidence indicates immunised people can have\u00a0high levels of virus in the nose, potentially as high as unvaccinated people.<\/span><\/p>\n

However, if you\u2019re vaccinated you\u2019ll clear the virus more quickly, reducing the length of time you\u2019re infectious and can pass the virus on.<\/span><\/p>\n

Here\u2019s why breakthrough cases are happening, and why you shouldn\u2019t worry too much.<\/span><\/p>\n

Waning immunity<\/strong><\/span><\/p>\n

Two studies from the United Kingdom suggest\u00a0the immunity we get from Covid vaccines wanes over time, after about four to six months.<\/span><\/p>\n

While the more-infectious Delta variant continues to circulate, waning immunity will\u00a0lead to more breakthrough infections.<\/span><\/p>\n

But the reduction isn\u2019t large currently. Vaccine effectiveness is very high to begin with, so incremental reductions due to waning won\u2019t have a significant effect on protection for some time.<\/span><\/p>\n

Israeli data shows\u00a0some vaccinated people are becoming ill with Covid. But we need to keep in mind Israel\u2019s vaccine rollout began in December 2020, and the majority of the population were vaccinated in early 2021. Most are now past six months since being fully vaccinated.<\/span><\/p>\n

Given most people in Israel are vaccinated, many Covid cases in hospital are vaccinated. However, the majority (87%) of hospitalised cases are 60 or older. This highlights what\u2019s known about adaptive immunity and vaccine protection \u2014 it declines with age.<\/span><\/p>\n

Therefore we\u2019d expect\u00a0vulnerable groups like the elderly\u00a0to be the first at risk of disease as immunity wanes, as will people whose immune systems are compromised. Managing this as we adjust to living with Covid will be an ongoing challenge for all countries.<\/span><\/p>\n

What would be concerning is if we started seeing a big increase in fully vaccinated people getting really sick and dying \u2014 but that\u2019s not happening.<\/span><\/p>\n

Globally, the vast majority of people with severe Covid are unvaccinated.<\/span><\/p>\n

We\u2019ll probably need booster doses<\/span><\/strong><\/p>\n

Waning immunity means booster doses will likely be needed to top up protection, at least for the next couple of years while the virus continues to circulate at such high levels.<\/span><\/p>\n

Our currently approved vaccines were modelled on the original strain of the virus isolated in Wuhan, not the Delta variant, which is currently dominant across most of the world. This imperfect match between vaccine and virus means\u00a0the level of protection against Delta is just a little lower.<\/span><\/p>\n

Because the level of effectiveness is so high to begin with, this small reduction is negligible in the short term. But the effects of waning over time may lead to breakthrough infections appearing sooner.<\/span><\/p>\n

mRNA vaccines in particular, like Pfizer\u2019s and Moderna\u2019s, can be efficiently updated to target prevalent variants, in this case Delta. So, a third immunisation based on Delta will \u201ctweak\u201d, as well as boost, existing immunity to an even higher starting point for longer-lasting protection.<\/span><\/p>\n

We could see different variants become endemic in different countries. One example might be the Mu variant, currently\u00a0dominant in Colombia. We might be able to match vaccines to whichever variant is circulating in specific areas.<\/span><\/p>\n

The dose makes the poison<\/strong><\/span><\/p>\n

Your\u00a0level of exposure\u00a0to the virus is likely another reason for breakthrough infections.<\/span><\/p>\n

If you\u2019re fully vaccinated and have merely fleeting contact with a positive case, you likely won\u2019t breathe in much virus and therefore are unlikely to develop symptomatic infection.<\/span><\/p>\n

But if you\u2019re in the same room as a positive case for a long period of time, you may breathe in a huge amount of virus. This makes it harder for your immune system to fight off.<\/span><\/p>\n

This may be one reason we\u2019re seeing\u00a0some health-care workers get breakthrough infections, because they\u2019re being exposed to high viral loads. They could be a priority for booster doses.<\/span><\/p>\n

Might unvaccinated kids be playing a role?<\/strong><\/span><\/p>\n

It\u2019s unclear if children are contributing to breakthrough infections.<\/span><\/p>\n

Vaccines aren\u2019t approved for young children yet (aged under 12), so we\u2019re seeing increasing cases in kids relative to older people. Early studies, before the rise of Delta, indicated children didn\u2019t significantly contribute to transmission.<\/span><\/p>\n

More recent studies in populations with vaccinated adults, and where Delta is the dominant virus, have suggested\u00a0children might contribute to transmission. This requires further investigation, but it\u2019s possible that if you\u2019re living with an unvaccinated child who contracts Covid, you\u2019re likely to be exposed for many, many hours of the day, hence you\u2019ll breathe in a large amount of virus.<\/span><\/p>\n

The larger the viral dose, the more likely you\u2019ll get a breakthrough infection.<\/span><\/p>\n

Potentially slowing the number of breakthrough infections is one reason to vaccinate 12 to 15 yearolds, and younger children in the future, if ongoing trials prove they\u2019re safe and effective in this age group. Another is to protect kids themselves, and to get closer to herd immunity (if it\u2019s achievable).<\/span><\/p>\n

A silver lining<\/strong><\/span><\/p>\n

Breakthrough infections likely\u00a0confer extra protection\u00a0for people who\u2019ve been fully vaccinated \u2014 almost like a booster dose.<\/span><\/p>\n

We don\u2019t have solid real-world data on this yet, but it\u00a0isn\u2019t surprising\u00a0as it\u2019s how our immune system works. Infection will re-expose the immune system to the virus\u2019 spike protein and boost antibodies against the spike.<\/span><\/p>\n

However, it\u2019s never advisable to get Covid, because you could get very sick or die. Extra protection is just a silver lining if you do get a breakthrough infection.<\/span><\/p>\n

As Covid becomes an endemic disease, meaning it settles into the human population, we\u2019ll need to keep a constant eye on the interaction between vaccines and the virus.<\/span><\/p>\n

The virus may start to burn out, but it\u2019s also possible it might continually evolve and evade vaccines, like the flu does.<\/span><\/p>\n

\n

* Published in print edition on 10 September 2021<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

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