NZX-listed AFT Pharmaceuticals sold $1.2 million worth of its vitamin C sachets over three days last week, managing director Dr Hartley Atkinson says - or the same dollar amount it sold over the previous year.
The larger, privately-held Douglas Pharmaceuticals, would not put a figure on it, but told the Herald it had also seen strong demand for vitamin C.
Atkinson, without making any claims for its ability to counter coronavirus himself, told the Herald he thought buyers were looking to boost their immune systems.
On its website, AFT says its Vitamin C Lipo-Sachets, which sell in $49.99 packs, "Support the *normal* function of the immune system" [the Herald's emphasis] and "Help to reduce the frequency and severity of colds and flu."
Douglas Pharmaceuticals says its Super Family C 550 (around $20 for 100 capsules) "Provides calcium ascorbate threonate, an esterified Vitamin C, which metabolises to provide 24 hour immune support".
(Both AFT and Douglas have dual lines of business: pharmaceuticals, plus nutrients or "nutraceuticals" such as vitamins.)
Is the rush of buyers correct to think vitamin C will help boost their immune system as they face the risk of Covid-19?
The Herald asked infectious disease expert Dr Mark Thomas, who is an associate professor at the University of Auckland (Faculty of Medical and Health Sciences) and a clinician at the Auckland District Health Board.
"Increased concerns about the threat posed by infections has often resulted in people taking non-prescription medicines, such as vitamin C, to try to prevent infection occurring, or enhance recovery from infection," Thomas said.
"However, many of the non-prescription medicines that are commonly promoted for these uses lack convincing evidence that they are useful.
"Many may be the modern equivalent of old fashioned remedies that are no longer used - modern versions of 'snake oil'.
"Given the very recent emergence of the novel coronavirus there will almost certainly be no evidence of the efficacy of any off-the-shelf medicines for Covid-19."
If you're still of a mind to keep stockpiling vitamin C, there doesn't seem to be any particular need.
AFT and Douglas Pharmaceuticals both say they have no immediate issues with any ingredients suppliers for either pharmaceuticals or nutraceuticals, in part because of stock-piling in the early days of the crisis.
Both have a mix of onshore and off-shore manufacturing, and source ingredients from a number of countries.
Vitamin C is China-centric, but even as the rest of the world braces, China has reported a slowdown in new cases.
In a note sent to institutional clients on March 11, Forsyth Barr said that outside of the Hubei province, where the virus originated, more than 90 per cent of large-scale industrial enterprises have returned to normal production.
Out of China's top 100 cities, 26 have completely resumed normal operation and another 66 have reached more than 90 per cent, ForBarr said.
Restaurants and shopping malls in major cities are gradually resuming normal operation with 90 per cent of restaurants open for business in Beijing and more than 80 per cent in Shanghai, Guangzhou, Shenzhen and Ningbo.
More than 80 per cent of shopping malls and supermarkets have reopened in Chengdu, Shanghai, Beijing, Guangzhou and Shenyang, the wealth manager said.
Another sign of progress is that Alibaba's Chinese delivery arm is back at pre-outbreak staffing levels while the postal service industry has achieved 92.5 per cent with more than 160 million express shipments being processed per day.
Even in Hubei province, some of the low risk cities have removed lock-downs, such as Qianjiang city, and are returning to work with checkpoints being lifted and public transport resuming.